Added wordpress

1 files changed, 3709 insertions, 0 deletions

diff --git a/srcs/wordpress/wp-includes/user.php b/srcs/wordpress/wp-includes/user.php
new file mode 100644
index 0000000..505048e
--- /dev/null
+++ b/srcs/wordpress/wp-includes/user.php
@@ -0,0 +1,3709 @@
+<?php
+/**
+ * Core User API
+ *
+ * @package WordPress
+ * @subpackage Users
+ */
+
+/**
+ * Authenticates and logs a user in with 'remember' capability.
+ *
+ * The credentials is an array that has 'user_login', 'user_password', and
+ * 'remember' indices. If the credentials is not given, then the log in form
+ * will be assumed and used if set.
+ *
+ * The various authentication cookies will be set by this function and will be
+ * set for a longer period depending on if the 'remember' credential is set to
+ * true.
+ *
+ * Note: wp_signon() doesn't handle setting the current user. This means that if the
+ * function is called before the {@see 'init'} hook is fired, is_user_logged_in() will
+ * evaluate as false until that point. If is_user_logged_in() is needed in conjunction
+ * with wp_signon(), wp_set_current_user() should be called explicitly.
+ *
+ * @since 2.5.0
+ *
+ * @global string $auth_secure_cookie
+ *
+ * @param array       $credentials   Optional. User info in order to sign on.
+ * @param string|bool $secure_cookie Optional. Whether to use secure cookie.
+ * @return WP_User|WP_Error WP_User on success, WP_Error on failure.
+ */
+function wp_signon( $credentials = array(), $secure_cookie = '' ) {
+	if ( empty( $credentials ) ) {
+		$credentials = array(); // Back-compat for plugins passing an empty string.
+
+		if ( ! empty( $_POST['log'] ) ) {
+			$credentials['user_login'] = $_POST['log'];
+		}
+		if ( ! empty( $_POST['pwd'] ) ) {
+			$credentials['user_password'] = $_POST['pwd'];
+		}
+		if ( ! empty( $_POST['rememberme'] ) ) {
+			$credentials['remember'] = $_POST['rememberme'];
+		}
+	}
+
+	if ( ! empty( $credentials['remember'] ) ) {
+		$credentials['remember'] = true;
+	} else {
+		$credentials['remember'] = false;
+	}
+
+	/**
+	 * Fires before the user is authenticated.
+	 *
+	 * The variables passed to the callbacks are passed by reference,
+	 * and can be modified by callback functions.
+	 *
+	 * @since 1.5.1
+	 *
+	 * @todo Decide whether to deprecate the wp_authenticate action.
+	 *
+	 * @param string $user_login    Username (passed by reference).
+	 * @param string $user_password User password (passed by reference).
+	 */
+	do_action_ref_array( 'wp_authenticate', array( &$credentials['user_login'], &$credentials['user_password'] ) );
+
+	if ( '' === $secure_cookie ) {
+		$secure_cookie = is_ssl();
+	}
+
+	/**
+	 * Filters whether to use a secure sign-on cookie.
+	 *
+	 * @since 3.1.0
+	 *
+	 * @param bool  $secure_cookie Whether to use a secure sign-on cookie.
+	 * @param array $credentials {
+	 *     Array of entered sign-on data.
+	 *
+	 *     @type string $user_login    Username.
+	 *     @type string $user_password Password entered.
+	 *     @type bool   $remember      Whether to 'remember' the user. Increases the time
+	 *                                 that the cookie will be kept. Default false.
+	 * }
+	 */
+	$secure_cookie = apply_filters( 'secure_signon_cookie', $secure_cookie, $credentials );
+
+	global $auth_secure_cookie; // XXX ugly hack to pass this to wp_authenticate_cookie
+	$auth_secure_cookie = $secure_cookie;
+
+	add_filter( 'authenticate', 'wp_authenticate_cookie', 30, 3 );
+
+	$user = wp_authenticate( $credentials['user_login'], $credentials['user_password'] );
+
+	if ( is_wp_error( $user ) ) {
+		return $user;
+	}
+
+	wp_set_auth_cookie( $user->ID, $credentials['remember'], $secure_cookie );
+	/**
+	 * Fires after the user has successfully logged in.
+	 *
+	 * @since 1.5.0
+	 *
+	 * @param string  $user_login Username.
+	 * @param WP_User $user       WP_User object of the logged-in user.
+	 */
+	do_action( 'wp_login', $user->user_login, $user );
+	return $user;
+}
+
+/**
+ * Authenticate a user, confirming the username and password are valid.
+ *
+ * @since 2.8.0
+ *
+ * @param WP_User|WP_Error|null $user     WP_User or WP_Error object from a previous callback. Default null.
+ * @param string                $username Username for authentication.
+ * @param string                $password Password for authentication.
+ * @return WP_User|WP_Error WP_User on success, WP_Error on failure.
+ */
+function wp_authenticate_username_password( $user, $username, $password ) {
+	if ( $user instanceof WP_User ) {
+		return $user;
+	}
+
+	if ( empty( $username ) || empty( $password ) ) {
+		if ( is_wp_error( $user ) ) {
+			return $user;
+		}
+
+		$error = new WP_Error();
+
+		if ( empty( $username ) ) {
+			$error->add( 'empty_username', __( '<strong>ERROR</strong>: The username field is empty.' ) );
+		}
+
+		if ( empty( $password ) ) {
+			$error->add( 'empty_password', __( '<strong>ERROR</strong>: The password field is empty.' ) );
+		}
+
+		return $error;
+	}
+
+	$user = get_user_by( 'login', $username );
+
+	if ( ! $user ) {
+		return new WP_Error(
+			'invalid_username',
+			__( 'Unknown username. Check again or try your email address.' )
+		);
+	}
+
+	/**
+	 * Filters whether the given user can be authenticated with the provided $password.
+	 *
+	 * @since 2.5.0
+	 *
+	 * @param WP_User|WP_Error $user     WP_User or WP_Error object if a previous
+	 *                                   callback failed authentication.
+	 * @param string           $password Password to check against the user.
+	 */
+	$user = apply_filters( 'wp_authenticate_user', $user, $password );
+	if ( is_wp_error( $user ) ) {
+		return $user;
+	}
+
+	if ( ! wp_check_password( $password, $user->user_pass, $user->ID ) ) {
+		return new WP_Error(
+			'incorrect_password',
+			sprintf(
+				/* translators: %s: User name. */
+				__( '<strong>ERROR</strong>: The password you entered for the username %s is incorrect.' ),
+				'<strong>' . $username . '</strong>'
+			) .
+			' <a href="' . wp_lostpassword_url() . '">' .
+			__( 'Lost your password?' ) .
+			'</a>'
+		);
+	}
+
+	return $user;
+}
+
+/**
+ * Authenticates a user using the email and password.
+ *
+ * @since 4.5.0
+ *
+ * @param WP_User|WP_Error|null $user     WP_User or WP_Error object if a previous
+ *                                        callback failed authentication.
+ * @param string                $email    Email address for authentication.
+ * @param string                $password Password for authentication.
+ * @return WP_User|WP_Error WP_User on success, WP_Error on failure.
+ */
+function wp_authenticate_email_password( $user, $email, $password ) {
+	if ( $user instanceof WP_User ) {
+		return $user;
+	}
+
+	if ( empty( $email ) || empty( $password ) ) {
+		if ( is_wp_error( $user ) ) {
+			return $user;
+		}
+
+		$error = new WP_Error();
+
+		if ( empty( $email ) ) {
+			$error->add( 'empty_username', __( '<strong>ERROR</strong>: The email field is empty.' ) ); // Uses 'empty_username' for back-compat with wp_signon()
+		}
+
+		if ( empty( $password ) ) {
+			$error->add( 'empty_password', __( '<strong>ERROR</strong>: The password field is empty.' ) );
+		}
+
+		return $error;
+	}
+
+	if ( ! is_email( $email ) ) {
+		return $user;
+	}
+
+	$user = get_user_by( 'email', $email );
+
+	if ( ! $user ) {
+		return new WP_Error(
+			'invalid_email',
+			__( 'Unknown email address. Check again or try your username.' )
+		);
+	}
+
+	/** This filter is documented in wp-includes/user.php */
+	$user = apply_filters( 'wp_authenticate_user', $user, $password );
+
+	if ( is_wp_error( $user ) ) {
+		return $user;
+	}
+
+	if ( ! wp_check_password( $password, $user->user_pass, $user->ID ) ) {
+		return new WP_Error(
+			'incorrect_password',
+			sprintf(
+				/* translators: %s: Email address. */
+				__( '<strong>ERROR</strong>: The password you entered for the email address %s is incorrect.' ),
+				'<strong>' . $email . '</strong>'
+			) .
+			' <a href="' . wp_lostpassword_url() . '">' .
+			__( 'Lost your password?' ) .
+			'</a>'
+		);
+	}
+
+	return $user;
+}
+
+/**
+ * Authenticate the user using the WordPress auth cookie.
+ *
+ * @since 2.8.0
+ *
+ * @global string $auth_secure_cookie
+ *
+ * @param WP_User|WP_Error|null $user     WP_User or WP_Error object from a previous callback. Default null.
+ * @param string                $username Username. If not empty, cancels the cookie authentication.
+ * @param string                $password Password. If not empty, cancels the cookie authentication.
+ * @return WP_User|WP_Error WP_User on success, WP_Error on failure.
+ */
+function wp_authenticate_cookie( $user, $username, $password ) {
+	if ( $user instanceof WP_User ) {
+		return $user;
+	}
+
+	if ( empty( $username ) && empty( $password ) ) {
+		$user_id = wp_validate_auth_cookie();
+		if ( $user_id ) {
+			return new WP_User( $user_id );
+		}
+
+		global $auth_secure_cookie;
+
+		if ( $auth_secure_cookie ) {
+			$auth_cookie = SECURE_AUTH_COOKIE;
+		} else {
+			$auth_cookie = AUTH_COOKIE;
+		}
+
+		if ( ! empty( $_COOKIE[ $auth_cookie ] ) ) {
+			return new WP_Error( 'expired_session', __( 'Please log in again.' ) );
+		}
+
+		// If the cookie is not set, be silent.
+	}
+
+	return $user;
+}
+
+/**
+ * For Multisite blogs, check if the authenticated user has been marked as a
+ * spammer, or if the user's primary blog has been marked as spam.
+ *
+ * @since 3.7.0
+ *
+ * @param WP_User|WP_Error|null $user WP_User or WP_Error object from a previous callback. Default null.
+ * @return WP_User|WP_Error WP_User on success, WP_Error if the user is considered a spammer.
+ */
+function wp_authenticate_spam_check( $user ) {
+	if ( $user instanceof WP_User && is_multisite() ) {
+		/**
+		 * Filters whether the user has been marked as a spammer.
+		 *
+		 * @since 3.7.0
+		 *
+		 * @param bool    $spammed Whether the user is considered a spammer.
+		 * @param WP_User $user    User to check against.
+		 */
+		$spammed = apply_filters( 'check_is_user_spammed', is_user_spammy( $user ), $user );
+
+		if ( $spammed ) {
+			return new WP_Error( 'spammer_account', __( '<strong>ERROR</strong>: Your account has been marked as a spammer.' ) );
+		}
+	}
+	return $user;
+}
+
+/**
+ * Validates the logged-in cookie.
+ *
+ * Checks the logged-in cookie if the previous auth cookie could not be
+ * validated and parsed.
+ *
+ * This is a callback for the {@see 'determine_current_user'} filter, rather than API.
+ *
+ * @since 3.9.0
+ *
+ * @param int|bool $user_id The user ID (or false) as received from the
+ *                       determine_current_user filter.
+ * @return int|false User ID if validated, false otherwise. If a user ID from
+ *                   an earlier filter callback is received, that value is returned.
+ */
+function wp_validate_logged_in_cookie( $user_id ) {
+	if ( $user_id ) {
+		return $user_id;
+	}
+
+	if ( is_blog_admin() || is_network_admin() || empty( $_COOKIE[ LOGGED_IN_COOKIE ] ) ) {
+		return false;
+	}
+
+	return wp_validate_auth_cookie( $_COOKIE[ LOGGED_IN_COOKIE ], 'logged_in' );
+}
+
+/**
+ * Number of posts user has written.
+ *
+ * @since 3.0.0
+ * @since 4.1.0 Added `$post_type` argument.
+ * @since 4.3.0 Added `$public_only` argument. Added the ability to pass an array
+ *              of post types to `$post_type`.
+ *
+ * @global wpdb $wpdb WordPress database abstraction object.
+ *
+ * @param int          $userid      User ID.
+ * @param array|string $post_type   Optional. Single post type or array of post types to count the number of posts for. Default 'post'.
+ * @param bool         $public_only Optional. Whether to only return counts for public posts. Default false.
+ * @return string Number of posts the user has written in this post type.
+ */
+function count_user_posts( $userid, $post_type = 'post', $public_only = false ) {
+	global $wpdb;
+
+	$where = get_posts_by_author_sql( $post_type, true, $userid, $public_only );
+
+	$count = $wpdb->get_var( "SELECT COUNT(*) FROM $wpdb->posts $where" );
+
+	/**
+	 * Filters the number of posts a user has written.
+	 *
+	 * @since 2.7.0
+	 * @since 4.1.0 Added `$post_type` argument.
+	 * @since 4.3.1 Added `$public_only` argument.
+	 *
+	 * @param int          $count       The user's post count.
+	 * @param int          $userid      User ID.
+	 * @param string|array $post_type   Single post type or array of post types to count the number of posts for.
+	 * @param bool         $public_only Whether to limit counted posts to public posts.
+	 */
+	return apply_filters( 'get_usernumposts', $count, $userid, $post_type, $public_only );
+}
+
+/**
+ * Number of posts written by a list of users.
+ *
+ * @since 3.0.0
+ *
+ * @global wpdb $wpdb WordPress database abstraction object.
+ *
+ * @param array        $users       Array of user IDs.
+ * @param string|array $post_type   Optional. Single post type or array of post types to check. Defaults to 'post'.
+ * @param bool         $public_only Optional. Only return counts for public posts.  Defaults to false.
+ * @return array Amount of posts each user has written.
+ */
+function count_many_users_posts( $users, $post_type = 'post', $public_only = false ) {
+	global $wpdb;
+
+	$count = array();
+	if ( empty( $users ) || ! is_array( $users ) ) {
+		return $count;
+	}
+
+	$userlist = implode( ',', array_map( 'absint', $users ) );
+	$where    = get_posts_by_author_sql( $post_type, true, null, $public_only );
+
+	$result = $wpdb->get_results( "SELECT post_author, COUNT(*) FROM $wpdb->posts $where AND post_author IN ($userlist) GROUP BY post_author", ARRAY_N );
+	foreach ( $result as $row ) {
+		$count[ $row[0] ] = $row[1];
+	}
+
+	foreach ( $users as $id ) {
+		if ( ! isset( $count[ $id ] ) ) {
+			$count[ $id ] = 0;
+		}
+	}
+
+	return $count;
+}
+
+//
+// User option functions
+//
+
+/**
+ * Get the current user's ID
+ *
+ * @since MU (3.0.0)
+ *
+ * @return int The current user's ID, or 0 if no user is logged in.
+ */
+function get_current_user_id() {
+	if ( ! function_exists( 'wp_get_current_user' ) ) {
+		return 0;
+	}
+	$user = wp_get_current_user();
+	return ( isset( $user->ID ) ? (int) $user->ID : 0 );
+}
+
+/**
+ * Retrieve user option that can be either per Site or per Network.
+ *
+ * If the user ID is not given, then the current user will be used instead. If
+ * the user ID is given, then the user data will be retrieved. The filter for
+ * the result, will also pass the original option name and finally the user data
+ * object as the third parameter.
+ *
+ * The option will first check for the per site name and then the per Network name.
+ *
+ * @since 2.0.0
+ *
+ * @global wpdb $wpdb WordPress database abstraction object.
+ *
+ * @param string $option     User option name.
+ * @param int    $user       Optional. User ID.
+ * @param string $deprecated Use get_option() to check for an option in the options table.
+ * @return mixed User option value on success, false on failure.
+ */
+function get_user_option( $option, $user = 0, $deprecated = '' ) {
+	global $wpdb;
+
+	if ( ! empty( $deprecated ) ) {
+		_deprecated_argument( __FUNCTION__, '3.0.0' );
+	}
+
+	if ( empty( $user ) ) {
+		$user = get_current_user_id();
+	}
+
+	$user = get_userdata( $user );
+	if ( ! $user ) {
+		return false;
+	}
+
+	$prefix = $wpdb->get_blog_prefix();
+	if ( $user->has_prop( $prefix . $option ) ) { // Blog specific
+		$result = $user->get( $prefix . $option );
+	} elseif ( $user->has_prop( $option ) ) { // User specific and cross-blog
+		$result = $user->get( $option );
+	} else {
+		$result = false;
+	}
+
+	/**
+	 * Filters a specific user option value.
+	 *
+	 * The dynamic portion of the hook name, `$option`, refers to the user option name.
+	 *
+	 * @since 2.5.0
+	 *
+	 * @param mixed   $result Value for the user's option.
+	 * @param string  $option Name of the option being retrieved.
+	 * @param WP_User $user   WP_User object of the user whose option is being retrieved.
+	 */
+	return apply_filters( "get_user_option_{$option}", $result, $option, $user );
+}
+
+/**
+ * Update user option with global blog capability.
+ *
+ * User options are just like user metadata except that they have support for
+ * global blog options. If the 'global' parameter is false, which it is by default
+ * it will prepend the WordPress table prefix to the option name.
+ *
+ * Deletes the user option if $newvalue is empty.
+ *
+ * @since 2.0.0
+ *
+ * @global wpdb $wpdb WordPress database abstraction object.
+ *
+ * @param int    $user_id     User ID.
+ * @param string $option_name User option name.
+ * @param mixed  $newvalue    User option value.
+ * @param bool   $global      Optional. Whether option name is global or blog specific.
+ *                            Default false (blog specific).
+ * @return int|bool User meta ID if the option didn't exist, true on successful update,
+ *                  false on failure.
+ */
+function update_user_option( $user_id, $option_name, $newvalue, $global = false ) {
+	global $wpdb;
+
+	if ( ! $global ) {
+		$option_name = $wpdb->get_blog_prefix() . $option_name;
+	}
+
+	return update_user_meta( $user_id, $option_name, $newvalue );
+}
+
+/**
+ * Delete user option with global blog capability.
+ *
+ * User options are just like user metadata except that they have support for
+ * global blog options. If the 'global' parameter is false, which it is by default
+ * it will prepend the WordPress table prefix to the option name.
+ *
+ * @since 3.0.0
+ *
+ * @global wpdb $wpdb WordPress database abstraction object.
+ *
+ * @param int    $user_id     User ID
+ * @param string $option_name User option name.
+ * @param bool   $global      Optional. Whether option name is global or blog specific.
+ *                            Default false (blog specific).
+ * @return bool True on success, false on failure.
+ */
+function delete_user_option( $user_id, $option_name, $global = false ) {
+	global $wpdb;
+
+	if ( ! $global ) {
+		$option_name = $wpdb->get_blog_prefix() . $option_name;
+	}
+	return delete_user_meta( $user_id, $option_name );
+}
+
+/**
+ * Retrieve list of users matching criteria.
+ *
+ * @since 3.1.0
+ *
+ * @see WP_User_Query
+ *
+ * @param array $args Optional. Arguments to retrieve users. See WP_User_Query::prepare_query().
+ *                    for more information on accepted arguments.
+ * @return array List of users.
+ */
+function get_users( $args = array() ) {
+
+	$args                = wp_parse_args( $args );
+	$args['count_total'] = false;
+
+	$user_search = new WP_User_Query( $args );
+
+	return (array) $user_search->get_results();
+}
+
+/**
+ * Get the sites a user belongs to.
+ *
+ * @since 3.0.0
+ * @since 4.7.0 Converted to use `get_sites()`.
+ *
+ * @global wpdb $wpdb WordPress database abstraction object.
+ *
+ * @param int  $user_id User ID
+ * @param bool $all     Whether to retrieve all sites, or only sites that are not
+ *                      marked as deleted, archived, or spam.
+ * @return array A list of the user's sites. An empty array if the user doesn't exist
+ *               or belongs to no sites.
+ */
+function get_blogs_of_user( $user_id, $all = false ) {
+	global $wpdb;
+
+	$user_id = (int) $user_id;
+
+	// Logged out users can't have sites
+	if ( empty( $user_id ) ) {
+		return array();
+	}
+
+	/**
+	 * Filters the list of a user's sites before it is populated.
+	 *
+	 * Passing a non-null value to the filter will effectively short circuit
+	 * get_blogs_of_user(), returning that value instead.
+	 *
+	 * @since 4.6.0
+	 *
+	 * @param null|array $sites   An array of site objects of which the user is a member.
+	 * @param int        $user_id User ID.
+	 * @param bool       $all     Whether the returned array should contain all sites, including
+	 *                            those marked 'deleted', 'archived', or 'spam'. Default false.
+	 */
+	$sites = apply_filters( 'pre_get_blogs_of_user', null, $user_id, $all );
+
+	if ( null !== $sites ) {
+		return $sites;
+	}
+
+	$keys = get_user_meta( $user_id );
+	if ( empty( $keys ) ) {
+		return array();
+	}
+
+	if ( ! is_multisite() ) {
+		$site_id                        = get_current_blog_id();
+		$sites                          = array( $site_id => new stdClass );
+		$sites[ $site_id ]->userblog_id = $site_id;
+		$sites[ $site_id ]->blogname    = get_option( 'blogname' );
+		$sites[ $site_id ]->domain      = '';
+		$sites[ $site_id ]->path        = '';
+		$sites[ $site_id ]->site_id     = 1;
+		$sites[ $site_id ]->siteurl     = get_option( 'siteurl' );
+		$sites[ $site_id ]->archived    = 0;
+		$sites[ $site_id ]->spam        = 0;
+		$sites[ $site_id ]->deleted     = 0;
+		return $sites;
+	}
+
+	$site_ids = array();
+
+	if ( isset( $keys[ $wpdb->base_prefix . 'capabilities' ] ) && defined( 'MULTISITE' ) ) {
+		$site_ids[] = 1;
+		unset( $keys[ $wpdb->base_prefix . 'capabilities' ] );
+	}
+
+	$keys = array_keys( $keys );
+
+	foreach ( $keys as $key ) {
+		if ( 'capabilities' !== substr( $key, -12 ) ) {
+			continue;
+		}
+		if ( $wpdb->base_prefix && 0 !== strpos( $key, $wpdb->base_prefix ) ) {
+			continue;
+		}
+		$site_id = str_replace( array( $wpdb->base_prefix, '_capabilities' ), '', $key );
+		if ( ! is_numeric( $site_id ) ) {
+			continue;
+		}
+
+		$site_ids[] = (int) $site_id;
+	}
+
+	$sites = array();
+
+	if ( ! empty( $site_ids ) ) {
+		$args = array(
+			'number'                 => '',
+			'site__in'               => $site_ids,
+			'update_site_meta_cache' => false,
+		);
+		if ( ! $all ) {
+			$args['archived'] = 0;
+			$args['spam']     = 0;
+			$args['deleted']  = 0;
+		}
+
+		$_sites = get_sites( $args );
+
+		foreach ( $_sites as $site ) {
+			$sites[ $site->id ] = (object) array(
+				'userblog_id' => $site->id,
+				'blogname'    => $site->blogname,
+				'domain'      => $site->domain,
+				'path'        => $site->path,
+				'site_id'     => $site->network_id,
+				'siteurl'     => $site->siteurl,
+				'archived'    => $site->archived,
+				'mature'      => $site->mature,
+				'spam'        => $site->spam,
+				'deleted'     => $site->deleted,
+			);
+		}
+	}
+
+	/**
+	 * Filters the list of sites a user belongs to.
+	 *
+	 * @since MU (3.0.0)
+	 *
+	 * @param array $sites   An array of site objects belonging to the user.
+	 * @param int   $user_id User ID.
+	 * @param bool  $all     Whether the returned sites array should contain all sites, including
+	 *                       those marked 'deleted', 'archived', or 'spam'. Default false.
+	 */
+	return apply_filters( 'get_blogs_of_user', $sites, $user_id, $all );
+}
+
+/**
+ * Find out whether a user is a member of a given blog.
+ *
+ * @since MU (3.0.0)
+ *
+ * @global wpdb $wpdb WordPress database abstraction object.
+ *
+ * @param int $user_id Optional. The unique ID of the user. Defaults to the current user.
+ * @param int $blog_id Optional. ID of the blog to check. Defaults to the current site.
+ * @return bool
+ */
+function is_user_member_of_blog( $user_id = 0, $blog_id = 0 ) {
+	global $wpdb;
+
+	$user_id = (int) $user_id;
+	$blog_id = (int) $blog_id;
+
+	if ( empty( $user_id ) ) {
+		$user_id = get_current_user_id();
+	}
+
+	// Technically not needed, but does save calls to get_site and get_user_meta
+	// in the event that the function is called when a user isn't logged in
+	if ( empty( $user_id ) ) {
+		return false;
+	} else {
+		$user = get_userdata( $user_id );
+		if ( ! $user instanceof WP_User ) {
+			return false;
+		}
+	}
+
+	if ( ! is_multisite() ) {
+		return true;
+	}
+
+	if ( empty( $blog_id ) ) {
+		$blog_id = get_current_blog_id();
+	}
+
+	$blog = get_site( $blog_id );
+
+	if ( ! $blog || ! isset( $blog->domain ) || $blog->archived || $blog->spam || $blog->deleted ) {
+		return false;
+	}
+
+	$keys = get_user_meta( $user_id );
+	if ( empty( $keys ) ) {
+		return false;
+	}
+
+	// no underscore before capabilities in $base_capabilities_key
+	$base_capabilities_key = $wpdb->base_prefix . 'capabilities';
+	$site_capabilities_key = $wpdb->base_prefix . $blog_id . '_capabilities';
+
+	if ( isset( $keys[ $base_capabilities_key ] ) && $blog_id == 1 ) {
+		return true;
+	}
+
+	if ( isset( $keys[ $site_capabilities_key ] ) ) {
+		return true;
+	}
+
+	return false;
+}
+
+/**
+ * Adds meta data to a user.
+ *
+ * @since 3.0.0
+ *
+ * @param int    $user_id    User ID.
+ * @param string $meta_key   Metadata name.
+ * @param mixed  $meta_value Metadata value.
+ * @param bool   $unique     Optional. Whether the same key should not be added. Default false.
+ * @return int|false Meta ID on success, false on failure.
+ */
+function add_user_meta( $user_id, $meta_key, $meta_value, $unique = false ) {
+	return add_metadata( 'user', $user_id, $meta_key, $meta_value, $unique );
+}
+
+/**
+ * Remove metadata matching criteria from a user.
+ *
+ * You can match based on the key, or key and value. Removing based on key and
+ * value, will keep from removing duplicate metadata with the same key. It also
+ * allows removing all metadata matching key, if needed.
+ *
+ * @since 3.0.0
+ * @link https://developer.wordpress.org/reference/functions/delete_user_meta/
+ *
+ * @param int    $user_id    User ID
+ * @param string $meta_key   Metadata name.
+ * @param mixed  $meta_value Optional. Metadata value.
+ * @return bool True on success, false on failure.
+ */
+function delete_user_meta( $user_id, $meta_key, $meta_value = '' ) {
+	return delete_metadata( 'user', $user_id, $meta_key, $meta_value );
+}
+
+/**
+ * Retrieve user meta field for a user.
+ *
+ * @since 3.0.0
+ * @link https://developer.wordpress.org/reference/functions/get_user_meta/
+ *
+ * @param int    $user_id User ID.
+ * @param string $key     Optional. The meta key to retrieve. By default, returns data for all keys.
+ * @param bool   $single  Whether to return a single value.
+ * @return mixed Will be an array if $single is false. Will be value of meta data field if $single is true.
+ */
+function get_user_meta( $user_id, $key = '', $single = false ) {
+	return get_metadata( 'user', $user_id, $key, $single );
+}
+
+/**
+ * Update user meta field based on user ID.
+ *
+ * Use the $prev_value parameter to differentiate between meta fields with the
+ * same key and user ID.
+ *
+ * If the meta field for the user does not exist, it will be added.
+ *
+ * @since 3.0.0
+ * @link https://developer.wordpress.org/reference/functions/update_user_meta/
+ *
+ * @param int    $user_id    User ID.
+ * @param string $meta_key   Metadata key.
+ * @param mixed  $meta_value Metadata value.
+ * @param mixed  $prev_value Optional. Previous value to check before removing.
+ * @return int|bool Meta ID if the key didn't exist, true on successful update, false on failure.
+ */
+function update_user_meta( $user_id, $meta_key, $meta_value, $prev_value = '' ) {
+	return update_metadata( 'user', $user_id, $meta_key, $meta_value, $prev_value );
+}
+
+/**
+ * Count number of users who have each of the user roles.
+ *
+ * Assumes there are neither duplicated nor orphaned capabilities meta_values.
+ * Assumes role names are unique phrases. Same assumption made by WP_User_Query::prepare_query()
+ * Using $strategy = 'time' this is CPU-intensive and should handle around 10^7 users.
+ * Using $strategy = 'memory' this is memory-intensive and should handle around 10^5 users, but see WP Bug #12257.
+ *
+ * @since 3.0.0
+ * @since 4.4.0 The number of users with no role is now included in the `none` element.
+ * @since 4.9.0 The `$site_id` parameter was added to support multisite.
+ *
+ * @global wpdb $wpdb WordPress database abstraction object.
+ *
+ * @param string   $strategy Optional. The computational strategy to use when counting the users.
+ *                           Accepts either 'time' or 'memory'. Default 'time'.
+ * @param int|null $site_id  Optional. The site ID to count users for. Defaults to the current site.
+ * @return array Includes a grand total and an array of counts indexed by role strings.
+ */
+function count_users( $strategy = 'time', $site_id = null ) {
+	global $wpdb;
+
+	// Initialize
+	if ( ! $site_id ) {
+		$site_id = get_current_blog_id();
+	}
+
+	/**
+	 * Filter the user count before queries are run. Return a non-null value to cause count_users()
+	 * to return early.
+	 *
+	 * @since 5.1.0
+	 *
+	 * @param null|string $result   Default null.
+	 * @param string      $strategy Optional. The computational strategy to use when counting the users.
+	 *                              Accepts either 'time' or 'memory'. Default 'time'.
+	 * @param int|null    $site_id  Optional. The site ID to count users for. Defaults to the current site.
+	 */
+	$pre = apply_filters( 'pre_count_users', null, $strategy, $site_id );
+
+	if ( null !== $pre ) {
+		return $pre;
+	}
+
+	$blog_prefix = $wpdb->get_blog_prefix( $site_id );
+	$result      = array();
+
+	if ( 'time' == $strategy ) {
+		if ( is_multisite() && $site_id != get_current_blog_id() ) {
+			switch_to_blog( $site_id );
+			$avail_roles = wp_roles()->get_names();
+			restore_current_blog();
+		} else {
+			$avail_roles = wp_roles()->get_names();
+		}
+
+		// Build a CPU-intensive query that will return concise information.
+		$select_count = array();
+		foreach ( $avail_roles as $this_role => $name ) {
+			$select_count[] = $wpdb->prepare( 'COUNT(NULLIF(`meta_value` LIKE %s, false))', '%' . $wpdb->esc_like( '"' . $this_role . '"' ) . '%' );
+		}
+		$select_count[] = "COUNT(NULLIF(`meta_value` = 'a:0:{}', false))";
+		$select_count   = implode( ', ', $select_count );
+
+		// Add the meta_value index to the selection list, then run the query.
+		$row = $wpdb->get_row(
+			"
+			SELECT {$select_count}, COUNT(*)
+			FROM {$wpdb->usermeta}
+			INNER JOIN {$wpdb->users} ON user_id = ID
+			WHERE meta_key = '{$blog_prefix}capabilities'
+		",
+			ARRAY_N
+		);
+
+		// Run the previous loop again to associate results with role names.
+		$col         = 0;
+		$role_counts = array();
+		foreach ( $avail_roles as $this_role => $name ) {
+			$count = (int) $row[ $col++ ];
+			if ( $count > 0 ) {
+				$role_counts[ $this_role ] = $count;
+			}
+		}
+
+		$role_counts['none'] = (int) $row[ $col++ ];
+
+		// Get the meta_value index from the end of the result set.
+		$total_users = (int) $row[ $col ];
+
+		$result['total_users'] = $total_users;
+		$result['avail_roles'] =& $role_counts;
+	} else {
+		$avail_roles = array(
+			'none' => 0,
+		);
+
+		$users_of_blog = $wpdb->get_col(
+			"
+			SELECT meta_value
+			FROM {$wpdb->usermeta}
+			INNER JOIN {$wpdb->users} ON user_id = ID
+			WHERE meta_key = '{$blog_prefix}capabilities'
+		"
+		);
+
+		foreach ( $users_of_blog as $caps_meta ) {
+			$b_roles = maybe_unserialize( $caps_meta );
+			if ( ! is_array( $b_roles ) ) {
+				continue;
+			}
+			if ( empty( $b_roles ) ) {
+				$avail_roles['none']++;
+			}
+			foreach ( $b_roles as $b_role => $val ) {
+				if ( isset( $avail_roles[ $b_role ] ) ) {
+					$avail_roles[ $b_role ]++;
+				} else {
+					$avail_roles[ $b_role ] = 1;
+				}
+			}
+		}
+
+		$result['total_users'] = count( $users_of_blog );
+		$result['avail_roles'] =& $avail_roles;
+	}
+
+	return $result;
+}
+
+//
+// Private helper functions
+//
+
+/**
+ * Set up global user vars.
+ *
+ * Used by wp_set_current_user() for back compat. Might be deprecated in the future.
+ *
+ * @since 2.0.4
+ *
+ * @global string  $user_login    The user username for logging in
+ * @global WP_User $userdata      User data.
+ * @global int     $user_level    The level of the user
+ * @global int     $user_ID       The ID of the user
+ * @global string  $user_email    The email address of the user
+ * @global string  $user_url      The url in the user's profile
+ * @global string  $user_identity The display name of the user
+ *
+ * @param int $for_user_id Optional. User ID to set up global data. Default 0.
+ */
+function setup_userdata( $for_user_id = 0 ) {
+	global $user_login, $userdata, $user_level, $user_ID, $user_email, $user_url, $user_identity;
+
+	if ( ! $for_user_id ) {
+		$for_user_id = get_current_user_id();
+	}
+	$user = get_userdata( $for_user_id );
+
+	if ( ! $user ) {
+		$user_ID       = 0;
+		$user_level    = 0;
+		$userdata      = null;
+		$user_login    = '';
+		$user_email    = '';
+		$user_url      = '';
+		$user_identity = '';
+		return;
+	}
+
+	$user_ID       = (int) $user->ID;
+	$user_level    = (int) $user->user_level;
+	$userdata      = $user;
+	$user_login    = $user->user_login;
+	$user_email    = $user->user_email;
+	$user_url      = $user->user_url;
+	$user_identity = $user->display_name;
+}
+
+/**
+ * Create dropdown HTML content of users.
+ *
+ * The content can either be displayed, which it is by default or retrieved by
+ * setting the 'echo' argument. The 'include' and 'exclude' arguments do not
+ * need to be used; all users will be displayed in that case. Only one can be
+ * used, either 'include' or 'exclude', but not both.
+ *
+ * The available arguments are as follows:
+ *
+ * @since 2.3.0
+ * @since 4.5.0 Added the 'display_name_with_login' value for 'show'.
+ * @since 4.7.0 Added the `$role`, `$role__in`, and `$role__not_in` parameters.
+ *
+ * @param array|string $args {
+ *     Optional. Array or string of arguments to generate a drop-down of users.
+ *     See WP_User_Query::prepare_query() for additional available arguments.
+ *
+ *     @type string       $show_option_all         Text to show as the drop-down default (all).
+ *                                                 Default empty.
+ *     @type string       $show_option_none        Text to show as the drop-down default when no
+ *                                                 users were found. Default empty.
+ *     @type int|string   $option_none_value       Value to use for $show_option_non when no users
+ *                                                 were found. Default -1.
+ *     @type string       $hide_if_only_one_author Whether to skip generating the drop-down
+ *                                                 if only one user was found. Default empty.
+ *     @type string       $orderby                 Field to order found users by. Accepts user fields.
+ *                                                 Default 'display_name'.
+ *     @type string       $order                   Whether to order users in ascending or descending
+ *                                                 order. Accepts 'ASC' (ascending) or 'DESC' (descending).
+ *                                                 Default 'ASC'.
+ *     @type array|string $include                 Array or comma-separated list of user IDs to include.
+ *                                                 Default empty.
+ *     @type array|string $exclude                 Array or comma-separated list of user IDs to exclude.
+ *                                                 Default empty.
+ *     @type bool|int     $multi                   Whether to skip the ID attribute on the 'select' element.
+ *                                                 Accepts 1|true or 0|false. Default 0|false.
+ *     @type string       $show                    User data to display. If the selected item is empty
+ *                                                 then the 'user_login' will be displayed in parentheses.
+ *                                                 Accepts any user field, or 'display_name_with_login' to show
+ *                                                 the display name with user_login in parentheses.
+ *                                                 Default 'display_name'.
+ *     @type int|bool     $echo                    Whether to echo or return the drop-down. Accepts 1|true (echo)
+ *                                                 or 0|false (return). Default 1|true.
+ *     @type int          $selected                Which user ID should be selected. Default 0.
+ *     @type bool         $include_selected        Whether to always include the selected user ID in the drop-
+ *                                                 down. Default false.
+ *     @type string       $name                    Name attribute of select element. Default 'user'.
+ *     @type string       $id                      ID attribute of the select element. Default is the value of $name.
+ *     @type string       $class                   Class attribute of the select element. Default empty.
+ *     @type int          $blog_id                 ID of blog (Multisite only). Default is ID of the current blog.
+ *     @type string       $who                     Which type of users to query. Accepts only an empty string or
+ *                                                 'authors'. Default empty.
+ *     @type string|array $role                    An array or a comma-separated list of role names that users must
+ *                                                 match to be included in results. Note that this is an inclusive
+ *                                                 list: users must match *each* role. Default empty.
+ *     @type array        $role__in                An array of role names. Matched users must have at least one of
+ *                                                 these roles. Default empty array.
+ *     @type array        $role__not_in            An array of role names to exclude. Users matching one or more of
+ *                                                 these roles will not be included in results. Default empty array.
+ * }
+ * @return string String of HTML content.
+ */
+function wp_dropdown_users( $args = '' ) {
+	$defaults = array(
+		'show_option_all'         => '',
+		'show_option_none'        => '',
+		'hide_if_only_one_author' => '',
+		'orderby'                 => 'display_name',
+		'order'                   => 'ASC',
+		'include'                 => '',
+		'exclude'                 => '',
+		'multi'                   => 0,
+		'show'                    => 'display_name',
+		'echo'                    => 1,
+		'selected'                => 0,
+		'name'                    => 'user',
+		'class'                   => '',
+		'id'                      => '',
+		'blog_id'                 => get_current_blog_id(),
+		'who'                     => '',
+		'include_selected'        => false,
+		'option_none_value'       => -1,
+		'role'                    => '',
+		'role__in'                => array(),
+		'role__not_in'            => array(),
+	);
+
+	$defaults['selected'] = is_author() ? get_query_var( 'author' ) : 0;
+
+	$parsed_args = wp_parse_args( $args, $defaults );
+
+	$query_args = wp_array_slice_assoc( $parsed_args, array( 'blog_id', 'include', 'exclude', 'orderby', 'order', 'who', 'role', 'role__in', 'role__not_in' ) );
+
+	$fields = array( 'ID', 'user_login' );
+
+	$show = ! empty( $parsed_args['show'] ) ? $parsed_args['show'] : 'display_name';
+	if ( 'display_name_with_login' === $show ) {
+		$fields[] = 'display_name';
+	} else {
+		$fields[] = $show;
+	}
+
+	$query_args['fields'] = $fields;
+
+	$show_option_all   = $parsed_args['show_option_all'];
+	$show_option_none  = $parsed_args['show_option_none'];
+	$option_none_value = $parsed_args['option_none_value'];
+
+	/**
+	 * Filters the query arguments for the list of users in the dropdown.
+	 *
+	 * @since 4.4.0
+	 *
+	 * @param array $query_args The query arguments for get_users().
+	 * @param array $parsed_args          The arguments passed to wp_dropdown_users() combined with the defaults.
+	 */
+	$query_args = apply_filters( 'wp_dropdown_users_args', $query_args, $parsed_args );
+
+	$users = get_users( $query_args );
+
+	$output = '';
+	if ( ! empty( $users ) && ( empty( $parsed_args['hide_if_only_one_author'] ) || count( $users ) > 1 ) ) {
+		$name = esc_attr( $parsed_args['name'] );
+		if ( $parsed_args['multi'] && ! $parsed_args['id'] ) {
+			$id = '';
+		} else {
+			$id = $parsed_args['id'] ? " id='" . esc_attr( $parsed_args['id'] ) . "'" : " id='$name'";
+		}
+		$output = "<select name='{$name}'{$id} class='" . $parsed_args['class'] . "'>\n";
+
+		if ( $show_option_all ) {
+			$output .= "\t<option value='0'>$show_option_all</option>\n";
+		}
+
+		if ( $show_option_none ) {
+			$_selected = selected( $option_none_value, $parsed_args['selected'], false );
+			$output   .= "\t<option value='" . esc_attr( $option_none_value ) . "'$_selected>$show_option_none</option>\n";
+		}
+
+		if ( $parsed_args['include_selected'] && ( $parsed_args['selected'] > 0 ) ) {
+			$found_selected          = false;
+			$parsed_args['selected'] = (int) $parsed_args['selected'];
+			foreach ( (array) $users as $user ) {
+				$user->ID = (int) $user->ID;
+				if ( $user->ID === $parsed_args['selected'] ) {
+					$found_selected = true;
+				}
+			}
+
+			if ( ! $found_selected ) {
+				$users[] = get_userdata( $parsed_args['selected'] );
+			}
+		}
+
+		foreach ( (array) $users as $user ) {
+			if ( 'display_name_with_login' === $show ) {
+				/* translators: 1: User's display name, 2: User login. */
+				$display = sprintf( _x( '%1$s (%2$s)', 'user dropdown' ), $user->display_name, $user->user_login );
+			} elseif ( ! empty( $user->$show ) ) {
+				$display = $user->$show;
+			} else {
+				$display = '(' . $user->user_login . ')';
+			}
+
+			$_selected = selected( $user->ID, $parsed_args['selected'], false );
+			$output   .= "\t<option value='$user->ID'$_selected>" . esc_html( $display ) . "</option>\n";
+		}
+
+		$output .= '</select>';
+	}
+
+	/**
+	 * Filters the wp_dropdown_users() HTML output.
+	 *
+	 * @since 2.3.0
+	 *
+	 * @param string $output HTML output generated by wp_dropdown_users().
+	 */
+	$html = apply_filters( 'wp_dropdown_users', $output );
+
+	if ( $parsed_args['echo'] ) {
+		echo $html;
+	}
+	return $html;
+}
+
+/**
+ * Sanitize user field based on context.
+ *
+ * Possible context values are:  'raw', 'edit', 'db', 'display', 'attribute' and 'js'. The
+ * 'display' context is used by default. 'attribute' and 'js' contexts are treated like 'display'
+ * when calling filters.
+ *
+ * @since 2.3.0
+ *
+ * @param string $field   The user Object field name.
+ * @param mixed  $value   The user Object value.
+ * @param int    $user_id User ID.
+ * @param string $context How to sanitize user fields. Looks for 'raw', 'edit', 'db', 'display',
+ *                        'attribute' and 'js'.
+ * @return mixed Sanitized value.
+ */
+function sanitize_user_field( $field, $value, $user_id, $context ) {
+	$int_fields = array( 'ID' );
+	if ( in_array( $field, $int_fields ) ) {
+		$value = (int) $value;
+	}
+
+	if ( 'raw' == $context ) {
+		return $value;
+	}
+
+	if ( ! is_string( $value ) && ! is_numeric( $value ) ) {
+		return $value;
+	}
+
+	$prefixed = false !== strpos( $field, 'user_' );
+
+	if ( 'edit' == $context ) {
+		if ( $prefixed ) {
+
+			/** This filter is documented in wp-includes/post.php */
+			$value = apply_filters( "edit_{$field}", $value, $user_id );
+		} else {
+
+			/**
+			 * Filters a user field value in the 'edit' context.
+			 *
+			 * The dynamic portion of the hook name, `$field`, refers to the prefixed user
+			 * field being filtered, such as 'user_login', 'user_email', 'first_name', etc.
+			 *
+			 * @since 2.9.0
+			 *
+			 * @param mixed $value   Value of the prefixed user field.
+			 * @param int   $user_id User ID.
+			 */
+			$value = apply_filters( "edit_user_{$field}", $value, $user_id );
+		}
+
+		if ( 'description' == $field ) {
+			$value = esc_html( $value ); // textarea_escaped?
+		} else {
+			$value = esc_attr( $value );
+		}
+	} elseif ( 'db' == $context ) {
+		if ( $prefixed ) {
+			/** This filter is documented in wp-includes/post.php */
+			$value = apply_filters( "pre_{$field}", $value );
+		} else {
+
+			/**
+			 * Filters the value of a user field in the 'db' context.
+			 *
+			 * The dynamic portion of the hook name, `$field`, refers to the prefixed user
+			 * field being filtered, such as 'user_login', 'user_email', 'first_name', etc.
+			 *
+			 * @since 2.9.0
+			 *
+			 * @param mixed $value Value of the prefixed user field.
+			 */
+			$value = apply_filters( "pre_user_{$field}", $value );
+		}
+	} else {
+		// Use display filters by default.
+		if ( $prefixed ) {
+
+			/** This filter is documented in wp-includes/post.php */
+			$value = apply_filters( "{$field}", $value, $user_id, $context );
+		} else {
+
+			/**
+			 * Filters the value of a user field in a standard context.
+			 *
+			 * The dynamic portion of the hook name, `$field`, refers to the prefixed user
+			 * field being filtered, such as 'user_login', 'user_email', 'first_name', etc.
+			 *
+			 * @since 2.9.0
+			 *
+			 * @param mixed  $value   The user object value to sanitize.
+			 * @param int    $user_id User ID.
+			 * @param string $context The context to filter within.
+			 */
+			$value = apply_filters( "user_{$field}", $value, $user_id, $context );
+		}
+	}
+
+	if ( 'user_url' == $field ) {
+		$value = esc_url( $value );
+	}
+
+	if ( 'attribute' == $context ) {
+		$value = esc_attr( $value );
+	} elseif ( 'js' == $context ) {
+		$value = esc_js( $value );
+	}
+	return $value;
+}
+
+/**
+ * Update all user caches
+ *
+ * @since 3.0.0
+ *
+ * @param WP_User $user User object to be cached
+ * @return bool|null Returns false on failure.
+ */
+function update_user_caches( $user ) {
+	if ( $user instanceof WP_User ) {
+		if ( ! $user->exists() ) {
+			return false;
+		}
+
+		$user = $user->data;
+	}
+
+	wp_cache_add( $user->ID, $user, 'users' );
+	wp_cache_add( $user->user_login, $user->ID, 'userlogins' );
+	wp_cache_add( $user->user_email, $user->ID, 'useremail' );
+	wp_cache_add( $user->user_nicename, $user->ID, 'userslugs' );
+}
+
+/**
+ * Clean all user caches
+ *
+ * @since 3.0.0
+ * @since 4.4.0 'clean_user_cache' action was added.
+ *
+ * @param WP_User|int $user User object or ID to be cleaned from the cache
+ */
+function clean_user_cache( $user ) {
+	if ( is_numeric( $user ) ) {
+		$user = new WP_User( $user );
+	}
+
+	if ( ! $user->exists() ) {
+		return;
+	}
+
+	wp_cache_delete( $user->ID, 'users' );
+	wp_cache_delete( $user->user_login, 'userlogins' );
+	wp_cache_delete( $user->user_email, 'useremail' );
+	wp_cache_delete( $user->user_nicename, 'userslugs' );
+
+	/**
+	 * Fires immediately after the given user's cache is cleaned.
+	 *
+	 * @since 4.4.0
+	 *
+	 * @param int     $user_id User ID.
+	 * @param WP_User $user    User object.
+	 */
+	do_action( 'clean_user_cache', $user->ID, $user );
+}
+
+/**
+ * Determines whether the given username exists.
+ *
+ * For more information on this and similar theme functions, check out
+ * the {@link https://developer.wordpress.org/themes/basics/conditional-tags/
+ * Conditional Tags} article in the Theme Developer Handbook.
+ *
+ * @since 2.0.0
+ *
+ * @param string $username Username.
+ * @return int|false The user's ID on success, and false on failure.
+ */
+function username_exists( $username ) {
+	$user = get_user_by( 'login', $username );
+	if ( $user ) {
+		$user_id = $user->ID;
+	} else {
+		$user_id = false;
+	}
+
+	/**
+	 * Filters whether the given username exists or not.
+	 *
+	 * @since 4.9.0
+	 *
+	 * @param int|false $user_id  The user's ID on success, and false on failure.
+	 * @param string    $username Username to check.
+	 */
+	return apply_filters( 'username_exists', $user_id, $username );
+}
+
+/**
+ * Determines whether the given email exists.
+ *
+ * For more information on this and similar theme functions, check out
+ * the {@link https://developer.wordpress.org/themes/basics/conditional-tags/
+ * Conditional Tags} article in the Theme Developer Handbook.
+ *
+ * @since 2.1.0
+ *
+ * @param string $email Email.
+ * @return int|false The user's ID on success, and false on failure.
+ */
+function email_exists( $email ) {
+	$user = get_user_by( 'email', $email );
+	if ( $user ) {
+		return $user->ID;
+	}
+	return false;
+}
+
+/**
+ * Checks whether a username is valid.
+ *
+ * @since 2.0.1
+ * @since 4.4.0 Empty sanitized usernames are now considered invalid
+ *
+ * @param string $username Username.
+ * @return bool Whether username given is valid
+ */
+function validate_username( $username ) {
+	$sanitized = sanitize_user( $username, true );
+	$valid     = ( $sanitized == $username && ! empty( $sanitized ) );
+
+	/**
+	 * Filters whether the provided username is valid or not.
+	 *
+	 * @since 2.0.1
+	 *
+	 * @param bool   $valid    Whether given username is valid.
+	 * @param string $username Username to check.
+	 */
+	return apply_filters( 'validate_username', $valid, $username );
+}
+
+/**
+ * Insert a user into the database.
+ *
+ * Most of the `$userdata` array fields have filters associated with the values. Exceptions are
+ * 'ID', 'rich_editing', 'syntax_highlighting', 'comment_shortcuts', 'admin_color', 'use_ssl',
+ * 'user_registered', 'user_activation_key', 'spam', and 'role'. The filters have the prefix
+ * 'pre_user_' followed by the field name. An example using 'description' would have the filter
+ * called 'pre_user_description' that can be hooked into.
+ *
+ * @since 2.0.0
+ * @since 3.6.0 The `aim`, `jabber`, and `yim` fields were removed as default user contact
+ *              methods for new installations. See wp_get_user_contact_methods().
+ * @since 4.7.0 The user's locale can be passed to `$userdata`.
+ * @since 5.3.0 The `user_activation_key` field can be passed to `$userdata`.
+ * @since 5.3.0 The `spam` field can be passed to `$userdata` (Multisite only).
+ *
+ * @global wpdb $wpdb WordPress database abstraction object.
+ *
+ * @param array|object|WP_User $userdata {
+ *     An array, object, or WP_User object of user data arguments.
+ *
+ *     @type int         $ID                   User ID. If supplied, the user will be updated.
+ *     @type string      $user_pass            The plain-text user password.
+ *     @type string      $user_login           The user's login username.
+ *     @type string      $user_nicename        The URL-friendly user name.
+ *     @type string      $user_url             The user URL.
+ *     @type string      $user_email           The user email address.
+ *     @type string      $display_name         The user's display name.
+ *                                             Default is the user's username.
+ *     @type string      $nickname             The user's nickname.
+ *                                             Default is the user's username.
+ *     @type string      $first_name           The user's first name. For new users, will be used
+ *                                             to build the first part of the user's display name
+ *                                             if `$display_name` is not specified.
+ *     @type string      $last_name            The user's last name. For new users, will be used
+ *                                             to build the second part of the user's display name
+ *                                             if `$display_name` is not specified.
+ *     @type string      $description          The user's biographical description.
+ *     @type string|bool $rich_editing         Whether to enable the rich-editor for the user.
+ *                                             False if not empty.
+ *     @type string|bool $syntax_highlighting  Whether to enable the rich code editor for the user.
+ *                                             False if not empty.
+ *     @type string|bool $comment_shortcuts    Whether to enable comment moderation keyboard
+ *                                             shortcuts for the user. Default false.
+ *     @type string      $admin_color          Admin color scheme for the user. Default 'fresh'.
+ *     @type bool        $use_ssl              Whether the user should always access the admin over
+ *                                             https. Default false.
+ *     @type string      $user_registered      Date the user registered. Format is 'Y-m-d H:i:s'.
+ *     @type string      $user_activation_key  Password reset key. Default empty.
+ *     @type bool        $spam                 Multisite only. Whether the user is marked as spam.
+ *                                             Default false.
+ *     @type string|bool $show_admin_bar_front Whether to display the Admin Bar for the user on the
+ *                                             site's front end. Default true.
+ *     @type string      $role                 User's role.
+ *     @type string      $locale               User's locale. Default empty.
+ * }
+ * @return int|WP_Error The newly created user's ID or a WP_Error object if the user could not
+ *                      be created.
+ */
+function wp_insert_user( $userdata ) {
+	global $wpdb;
+
+	if ( $userdata instanceof stdClass ) {
+		$userdata = get_object_vars( $userdata );
+	} elseif ( $userdata instanceof WP_User ) {
+		$userdata = $userdata->to_array();
+	}
+
+	// Are we updating or creating?
+	if ( ! empty( $userdata['ID'] ) ) {
+		$ID            = (int) $userdata['ID'];
+		$update        = true;
+		$old_user_data = get_userdata( $ID );
+
+		if ( ! $old_user_data ) {
+			return new WP_Error( 'invalid_user_id', __( 'Invalid user ID.' ) );
+		}
+
+		// hashed in wp_update_user(), plaintext if called directly
+		$user_pass = ! empty( $userdata['user_pass'] ) ? $userdata['user_pass'] : $old_user_data->user_pass;
+	} else {
+		$update = false;
+		// Hash the password
+		$user_pass = wp_hash_password( $userdata['user_pass'] );
+	}
+
+	$sanitized_user_login = sanitize_user( $userdata['user_login'], true );
+
+	/**
+	 * Filters a username after it has been sanitized.
+	 *
+	 * This filter is called before the user is created or updated.
+	 *
+	 * @since 2.0.3
+	 *
+	 * @param string $sanitized_user_login Username after it has been sanitized.
+	 */
+	$pre_user_login = apply_filters( 'pre_user_login', $sanitized_user_login );
+
+	//Remove any non-printable chars from the login string to see if we have ended up with an empty username
+	$user_login = trim( $pre_user_login );
+
+	// user_login must be between 0 and 60 characters.
+	if ( empty( $user_login ) ) {
+		return new WP_Error( 'empty_user_login', __( 'Cannot create a user with an empty login name.' ) );
+	} elseif ( mb_strlen( $user_login ) > 60 ) {
+		return new WP_Error( 'user_login_too_long', __( 'Username may not be longer than 60 characters.' ) );
+	}
+
+	if ( ! $update && username_exists( $user_login ) ) {
+		return new WP_Error( 'existing_user_login', __( 'Sorry, that username already exists!' ) );
+	}
+
+	/**
+	 * Filters the list of blacklisted usernames.
+	 *
+	 * @since 4.4.0
+	 *
+	 * @param array $usernames Array of blacklisted usernames.
+	 */
+	$illegal_logins = (array) apply_filters( 'illegal_user_logins', array() );
+
+	if ( in_array( strtolower( $user_login ), array_map( 'strtolower', $illegal_logins ) ) ) {
+		return new WP_Error( 'invalid_username', __( 'Sorry, that username is not allowed.' ) );
+	}
+
+	/*
+	 * If a nicename is provided, remove unsafe user characters before using it.
+	 * Otherwise build a nicename from the user_login.
+	 */
+	if ( ! empty( $userdata['user_nicename'] ) ) {
+		$user_nicename = sanitize_user( $userdata['user_nicename'], true );
+		if ( mb_strlen( $user_nicename ) > 50 ) {
+			return new WP_Error( 'user_nicename_too_long', __( 'Nicename may not be longer than 50 characters.' ) );
+		}
+	} else {
+		$user_nicename = mb_substr( $user_login, 0, 50 );
+	}
+
+	$user_nicename = sanitize_title( $user_nicename );
+
+	/**
+	 * Filters a user's nicename before the user is created or updated.
+	 *
+	 * @since 2.0.3
+	 *
+	 * @param string $user_nicename The user's nicename.
+	 */
+	$user_nicename = apply_filters( 'pre_user_nicename', $user_nicename );
+
+	$user_nicename_check = $wpdb->get_var( $wpdb->prepare( "SELECT ID FROM $wpdb->users WHERE user_nicename = %s AND user_login != %s LIMIT 1", $user_nicename, $user_login ) );
+
+	if ( $user_nicename_check ) {
+		$suffix = 2;
+		while ( $user_nicename_check ) {
+			// user_nicename allows 50 chars. Subtract one for a hyphen, plus the length of the suffix.
+			$base_length         = 49 - mb_strlen( $suffix );
+			$alt_user_nicename   = mb_substr( $user_nicename, 0, $base_length ) . "-$suffix";
+			$user_nicename_check = $wpdb->get_var( $wpdb->prepare( "SELECT ID FROM $wpdb->users WHERE user_nicename = %s AND user_login != %s LIMIT 1", $alt_user_nicename, $user_login ) );
+			$suffix++;
+		}
+		$user_nicename = $alt_user_nicename;
+	}
+
+	$raw_user_email = empty( $userdata['user_email'] ) ? '' : $userdata['user_email'];
+
+	/**
+	 * Filters a user's email before the user is created or updated.
+	 *
+	 * @since 2.0.3
+	 *
+	 * @param string $raw_user_email The user's email.
+	 */
+	$user_email = apply_filters( 'pre_user_email', $raw_user_email );
+
+	/*
+	 * If there is no update, just check for `email_exists`. If there is an update,
+	 * check if current email and new email are the same, or not, and check `email_exists`
+	 * accordingly.
+	 */
+	if ( ( ! $update || ( ! empty( $old_user_data ) && 0 !== strcasecmp( $user_email, $old_user_data->user_email ) ) )
+		&& ! defined( 'WP_IMPORTING' )
+		&& email_exists( $user_email )
+	) {
+		return new WP_Error( 'existing_user_email', __( 'Sorry, that email address is already used!' ) );
+	}
+
+	$raw_user_url = empty( $userdata['user_url'] ) ? '' : $userdata['user_url'];
+
+	/**
+	 * Filters a user's URL before the user is created or updated.
+	 *
+	 * @since 2.0.3
+	 *
+	 * @param string $raw_user_url The user's URL.
+	 */
+	$user_url = apply_filters( 'pre_user_url', $raw_user_url );
+
+	$user_registered = empty( $userdata['user_registered'] ) ? gmdate( 'Y-m-d H:i:s' ) : $userdata['user_registered'];
+
+	$user_activation_key = empty( $userdata['user_activation_key'] ) ? '' : $userdata['user_activation_key'];
+
+	if ( ! empty( $userdata['spam'] ) && ! is_multisite() ) {
+		return new WP_Error( 'no_spam', __( 'Sorry, marking a user as spam is only supported on Multisite.' ) );
+	}
+
+	$spam = empty( $userdata['spam'] ) ? 0 : (bool) $userdata['spam'];
+
+	// Store values to save in user meta.
+	$meta = array();
+
+	$nickname = empty( $userdata['nickname'] ) ? $user_login : $userdata['nickname'];
+
+	/**
+	 * Filters a user's nickname before the user is created or updated.
+	 *
+	 * @since 2.0.3
+	 *
+	 * @param string $nickname The user's nickname.
+	 */
+	$meta['nickname'] = apply_filters( 'pre_user_nickname', $nickname );
+
+	$first_name = empty( $userdata['first_name'] ) ? '' : $userdata['first_name'];
+
+	/**
+	 * Filters a user's first name before the user is created or updated.
+	 *
+	 * @since 2.0.3
+	 *
+	 * @param string $first_name The user's first name.
+	 */
+	$meta['first_name'] = apply_filters( 'pre_user_first_name', $first_name );
+
+	$last_name = empty( $userdata['last_name'] ) ? '' : $userdata['last_name'];
+
+	/**
+	 * Filters a user's last name before the user is created or updated.
+	 *
+	 * @since 2.0.3
+	 *
+	 * @param string $last_name The user's last name.
+	 */
+	$meta['last_name'] = apply_filters( 'pre_user_last_name', $last_name );
+
+	if ( empty( $userdata['display_name'] ) ) {
+		if ( $update ) {
+			$display_name = $user_login;
+		} elseif ( $meta['first_name'] && $meta['last_name'] ) {
+			/* translators: 1: User's first name, 2: Last name. */
+			$display_name = sprintf( _x( '%1$s %2$s', 'Display name based on first name and last name' ), $meta['first_name'], $meta['last_name'] );
+		} elseif ( $meta['first_name'] ) {
+			$display_name = $meta['first_name'];
+		} elseif ( $meta['last_name'] ) {
+			$display_name = $meta['last_name'];
+		} else {
+			$display_name = $user_login;
+		}
+	} else {
+		$display_name = $userdata['display_name'];
+	}
+
+	/**
+	 * Filters a user's display name before the user is created or updated.
+	 *
+	 * @since 2.0.3
+	 *
+	 * @param string $display_name The user's display name.
+	 */
+	$display_name = apply_filters( 'pre_user_display_name', $display_name );
+
+	$description = empty( $userdata['description'] ) ? '' : $userdata['description'];
+
+	/**
+	 * Filters a user's description before the user is created or updated.
+	 *
+	 * @since 2.0.3
+	 *
+	 * @param string $description The user's description.
+	 */
+	$meta['description'] = apply_filters( 'pre_user_description', $description );
+
+	$meta['rich_editing'] = empty( $userdata['rich_editing'] ) ? 'true' : $userdata['rich_editing'];
+
+	$meta['syntax_highlighting'] = empty( $userdata['syntax_highlighting'] ) ? 'true' : $userdata['syntax_highlighting'];
+
+	$meta['comment_shortcuts'] = empty( $userdata['comment_shortcuts'] ) || 'false' === $userdata['comment_shortcuts'] ? 'false' : 'true';
+
+	$admin_color         = empty( $userdata['admin_color'] ) ? 'fresh' : $userdata['admin_color'];
+	$meta['admin_color'] = preg_replace( '|[^a-z0-9 _.\-@]|i', '', $admin_color );
+
+	$meta['use_ssl'] = empty( $userdata['use_ssl'] ) ? 0 : (bool) $userdata['use_ssl'];
+
+	$meta['show_admin_bar_front'] = empty( $userdata['show_admin_bar_front'] ) ? 'true' : $userdata['show_admin_bar_front'];
+
+	$meta['locale'] = isset( $userdata['locale'] ) ? $userdata['locale'] : '';
+
+	$compacted = compact( 'user_pass', 'user_nicename', 'user_email', 'user_url', 'user_registered', 'user_activation_key', 'display_name' );
+	$data      = wp_unslash( $compacted );
+
+	if ( ! $update ) {
+		$data = $data + compact( 'user_login' );
+	}
+
+	if ( is_multisite() ) {
+		$data = $data + compact( 'spam' );
+	}
+
+	/**
+	 * Filters user data before the record is created or updated.
+	 *
+	 * It only includes data in the wp_users table wp_user, not any user metadata.
+	 *
+	 * @since 4.9.0
+	 *
+	 * @param array    $data {
+	 *     Values and keys for the user.
+	 *
+	 *     @type string $user_login      The user's login. Only included if $update == false
+	 *     @type string $user_pass       The user's password.
+	 *     @type string $user_email      The user's email.
+	 *     @type string $user_url        The user's url.
+	 *     @type string $user_nicename   The user's nice name. Defaults to a URL-safe version of user's login
+	 *     @type string $display_name    The user's display name.
+	 *     @type string $user_registered MySQL timestamp describing the moment when the user registered. Defaults to
+	 *                                   the current UTC timestamp.
+	 * }
+	 * @param bool     $update Whether the user is being updated rather than created.
+	 * @param int|null $id     ID of the user to be updated, or NULL if the user is being created.
+	 */
+	$data = apply_filters( 'wp_pre_insert_user_data', $data, $update, $update ? (int) $ID : null );
+
+	if ( empty( $data ) || ! is_array( $data ) ) {
+		return new WP_Error( 'empty_data', __( 'Not enough data to create this user.' ) );
+	}
+
+	if ( $update ) {
+		if ( $user_email !== $old_user_data->user_email ) {
+			$data['user_activation_key'] = '';
+		}
+		$wpdb->update( $wpdb->users, $data, compact( 'ID' ) );
+		$user_id = (int) $ID;
+	} else {
+		$wpdb->insert( $wpdb->users, $data );
+		$user_id = (int) $wpdb->insert_id;
+	}
+
+	$user = new WP_User( $user_id );
+
+	/**
+	 * Filters a user's meta values and keys immediately after the user is created or updated
+	 * and before any user meta is inserted or updated.
+	 *
+	 * Does not include contact methods. These are added using `wp_get_user_contact_methods( $user )`.
+	 *
+	 * @since 4.4.0
+	 *
+	 * @param array $meta {
+	 *     Default meta values and keys for the user.
+	 *
+	 *     @type string   $nickname             The user's nickname. Default is the user's username.
+	 *     @type string   $first_name           The user's first name.
+	 *     @type string   $last_name            The user's last name.
+	 *     @type string   $description          The user's description.
+	 *     @type bool     $rich_editing         Whether to enable the rich-editor for the user. False if not empty.
+	 *     @type bool     $syntax_highlighting  Whether to enable the rich code editor for the user. False if not empty.
+	 *     @type bool     $comment_shortcuts    Whether to enable keyboard shortcuts for the user. Default false.
+	 *     @type string   $admin_color          The color scheme for a user's admin screen. Default 'fresh'.
+	 *     @type int|bool $use_ssl              Whether to force SSL on the user's admin area. 0|false if SSL is
+	 *                                          not forced.
+	 *     @type bool     $show_admin_bar_front Whether to show the admin bar on the front end for the user.
+	 *                                          Default true.
+	 *     @type string   $locale               User's locale. Default empty.
+	 * }
+	 * @param WP_User $user   User object.
+	 * @param bool    $update Whether the user is being updated rather than created.
+	 */
+	$meta = apply_filters( 'insert_user_meta', $meta, $user, $update );
+
+	// Update user meta.
+	foreach ( $meta as $key => $value ) {
+		update_user_meta( $user_id, $key, $value );
+	}
+
+	foreach ( wp_get_user_contact_methods( $user ) as $key => $value ) {
+		if ( isset( $userdata[ $key ] ) ) {
+			update_user_meta( $user_id, $key, $userdata[ $key ] );
+		}
+	}
+
+	if ( isset( $userdata['role'] ) ) {
+		$user->set_role( $userdata['role'] );
+	} elseif ( ! $update ) {
+		$user->set_role( get_option( 'default_role' ) );
+	}
+
+	clean_user_cache( $user_id );
+
+	if ( $update ) {
+		/**
+		 * Fires immediately after an existing user is updated.
+		 *
+		 * @since 2.0.0
+		 *
+		 * @param int     $user_id       User ID.
+		 * @param WP_User $old_user_data Object containing user's data prior to update.
+		 */
+		do_action( 'profile_update', $user_id, $old_user_data );
+
+		if ( isset( $userdata['spam'] ) && $userdata['spam'] != $old_user_data->spam ) {
+			if ( $userdata['spam'] == 1 ) {
+				/**
+				 * Fires after the user is marked as a SPAM user.
+				 *
+				 * @since 3.0.0
+				 *
+				 * @param int $user_id ID of the user marked as SPAM.
+				 */
+				do_action( 'make_spam_user', $user_id );
+			} else {
+				/**
+				 * Fires after the user is marked as a HAM user. Opposite of SPAM.
+				 *
+				 * @since 3.0.0
+				 *
+				 * @param int $user_id ID of the user marked as HAM.
+				 */
+				do_action( 'make_ham_user', $user_id );
+			}
+		}
+	} else {
+		/**
+		 * Fires immediately after a new user is registered.
+		 *
+		 * @since 1.5.0
+		 *
+		 * @param int $user_id User ID.
+		 */
+		do_action( 'user_register', $user_id );
+	}
+
+	return $user_id;
+}
+
+/**
+ * Update a user in the database.
+ *
+ * It is possible to update a user's password by specifying the 'user_pass'
+ * value in the $userdata parameter array.
+ *
+ * If current user's password is being updated, then the cookies will be
+ * cleared.
+ *
+ * @since 2.0.0
+ *
+ * @see wp_insert_user() For what fields can be set in $userdata.
+ *
+ * @param array|object|WP_User $userdata An array of user data or a user object of type stdClass or WP_User.
+ * @return int|WP_Error The updated user's ID or a WP_Error object if the user could not be updated.
+ */
+function wp_update_user( $userdata ) {
+	if ( $userdata instanceof stdClass ) {
+		$userdata = get_object_vars( $userdata );
+	} elseif ( $userdata instanceof WP_User ) {
+		$userdata = $userdata->to_array();
+	}
+
+	$ID = isset( $userdata['ID'] ) ? (int) $userdata['ID'] : 0;
+	if ( ! $ID ) {
+		return new WP_Error( 'invalid_user_id', __( 'Invalid user ID.' ) );
+	}
+
+	// First, get all of the original fields
+	$user_obj = get_userdata( $ID );
+	if ( ! $user_obj ) {
+		return new WP_Error( 'invalid_user_id', __( 'Invalid user ID.' ) );
+	}
+
+	$user = $user_obj->to_array();
+
+	// Add additional custom fields
+	foreach ( _get_additional_user_keys( $user_obj ) as $key ) {
+		$user[ $key ] = get_user_meta( $ID, $key, true );
+	}
+
+	// Escape data pulled from DB.
+	$user = add_magic_quotes( $user );
+
+	if ( ! empty( $userdata['user_pass'] ) && $userdata['user_pass'] !== $user_obj->user_pass ) {
+		// If password is changing, hash it now
+		$plaintext_pass        = $userdata['user_pass'];
+		$userdata['user_pass'] = wp_hash_password( $userdata['user_pass'] );
+
+		/**
+		 * Filters whether to send the password change email.
+		 *
+		 * @since 4.3.0
+		 *
+		 * @see wp_insert_user() For `$user` and `$userdata` fields.
+		 *
+		 * @param bool  $send     Whether to send the email.
+		 * @param array $user     The original user array.
+		 * @param array $userdata The updated user array.
+		 */
+		$send_password_change_email = apply_filters( 'send_password_change_email', true, $user, $userdata );
+	}
+
+	if ( isset( $userdata['user_email'] ) && $user['user_email'] !== $userdata['user_email'] ) {
+		/**
+		 * Filters whether to send the email change email.
+		 *
+		 * @since 4.3.0
+		 *
+		 * @see wp_insert_user() For `$user` and `$userdata` fields.
+		 *
+		 * @param bool  $send     Whether to send the email.
+		 * @param array $user     The original user array.
+		 * @param array $userdata The updated user array.
+		 */
+		$send_email_change_email = apply_filters( 'send_email_change_email', true, $user, $userdata );
+	}
+
+	clean_user_cache( $user_obj );
+
+	// Merge old and new fields with new fields overwriting old ones.
+	$userdata = array_merge( $user, $userdata );
+	$user_id  = wp_insert_user( $userdata );
+
+	if ( ! is_wp_error( $user_id ) ) {
+
+		$blog_name = wp_specialchars_decode( get_option( 'blogname' ), ENT_QUOTES );
+
+		$switched_locale = false;
+		if ( ! empty( $send_password_change_email ) || ! empty( $send_email_change_email ) ) {
+			$switched_locale = switch_to_locale( get_user_locale( $user_id ) );
+		}
+
+		if ( ! empty( $send_password_change_email ) ) {
+			/* translators: Do not translate USERNAME, ADMIN_EMAIL, EMAIL, SITENAME, SITEURL: those are placeholders. */
+			$pass_change_text = __(
+				'Hi ###USERNAME###,
+
+This notice confirms that your password was changed on ###SITENAME###.
+
+If you did not change your password, please contact the Site Administrator at
+###ADMIN_EMAIL###
+
+This email has been sent to ###EMAIL###
+
+Regards,
+All at ###SITENAME###
+###SITEURL###'
+			);
+
+			$pass_change_email = array(
+				'to'      => $user['user_email'],
+				/* translators: Password change notification email subject. %s: Site title. */
+				'subject' => __( '[%s] Password Changed' ),
+				'message' => $pass_change_text,
+				'headers' => '',
+			);
+
+			/**
+			 * Filters the contents of the email sent when the user's password is changed.
+			 *
+			 * @since 4.3.0
+			 *
+			 * @param array $pass_change_email {
+			 *            Used to build wp_mail().
+			 *            @type string $to      The intended recipients. Add emails in a comma separated string.
+			 *            @type string $subject The subject of the email.
+			 *            @type string $message The content of the email.
+			 *                The following strings have a special meaning and will get replaced dynamically:
+			 *                - ###USERNAME###    The current user's username.
+			 *                - ###ADMIN_EMAIL### The admin email in case this was unexpected.
+			 *                - ###EMAIL###       The user's email address.
+			 *                - ###SITENAME###    The name of the site.
+			 *                - ###SITEURL###     The URL to the site.
+			 *            @type string $headers Headers. Add headers in a newline (\r\n) separated string.
+			 *        }
+			 * @param array $user     The original user array.
+			 * @param array $userdata The updated user array.
+			 */
+			$pass_change_email = apply_filters( 'password_change_email', $pass_change_email, $user, $userdata );
+
+			$pass_change_email['message'] = str_replace( '###USERNAME###', $user['user_login'], $pass_change_email['message'] );
+			$pass_change_email['message'] = str_replace( '###ADMIN_EMAIL###', get_option( 'admin_email' ), $pass_change_email['message'] );
+			$pass_change_email['message'] = str_replace( '###EMAIL###', $user['user_email'], $pass_change_email['message'] );
+			$pass_change_email['message'] = str_replace( '###SITENAME###', $blog_name, $pass_change_email['message'] );
+			$pass_change_email['message'] = str_replace( '###SITEURL###', home_url(), $pass_change_email['message'] );
+
+			wp_mail( $pass_change_email['to'], sprintf( $pass_change_email['subject'], $blog_name ), $pass_change_email['message'], $pass_change_email['headers'] );
+		}
+
+		if ( ! empty( $send_email_change_email ) ) {
+			/* translators: Do not translate USERNAME, ADMIN_EMAIL, NEW_EMAIL, EMAIL, SITENAME, SITEURL: those are placeholders. */
+			$email_change_text = __(
+				'Hi ###USERNAME###,
+
+This notice confirms that your email address on ###SITENAME### was changed to ###NEW_EMAIL###.
+
+If you did not change your email, please contact the Site Administrator at
+###ADMIN_EMAIL###
+
+This email has been sent to ###EMAIL###
+
+Regards,
+All at ###SITENAME###
+###SITEURL###'
+			);
+
+			$email_change_email = array(
+				'to'      => $user['user_email'],
+				/* translators: Email change notification email subject. %s: Site title. */
+				'subject' => __( '[%s] Email Changed' ),
+				'message' => $email_change_text,
+				'headers' => '',
+			);
+
+			/**
+			 * Filters the contents of the email sent when the user's email is changed.
+			 *
+			 * @since 4.3.0
+			 *
+			 * @param array $email_change_email {
+			 *            Used to build wp_mail().
+			 *            @type string $to      The intended recipients.
+			 *            @type string $subject The subject of the email.
+			 *            @type string $message The content of the email.
+			 *                The following strings have a special meaning and will get replaced dynamically:
+			 *                - ###USERNAME###    The current user's username.
+			 *                - ###ADMIN_EMAIL### The admin email in case this was unexpected.
+			 *                - ###NEW_EMAIL###   The new email address.
+			 *                - ###EMAIL###       The old email address.
+			 *                - ###SITENAME###    The name of the site.
+			 *                - ###SITEURL###     The URL to the site.
+			 *            @type string $headers Headers.
+			 *        }
+			 * @param array $user The original user array.
+			 * @param array $userdata The updated user array.
+			 */
+			$email_change_email = apply_filters( 'email_change_email', $email_change_email, $user, $userdata );
+
+			$email_change_email['message'] = str_replace( '###USERNAME###', $user['user_login'], $email_change_email['message'] );
+			$email_change_email['message'] = str_replace( '###ADMIN_EMAIL###', get_option( 'admin_email' ), $email_change_email['message'] );
+			$email_change_email['message'] = str_replace( '###NEW_EMAIL###', $userdata['user_email'], $email_change_email['message'] );
+			$email_change_email['message'] = str_replace( '###EMAIL###', $user['user_email'], $email_change_email['message'] );
+			$email_change_email['message'] = str_replace( '###SITENAME###', $blog_name, $email_change_email['message'] );
+			$email_change_email['message'] = str_replace( '###SITEURL###', home_url(), $email_change_email['message'] );
+
+			wp_mail( $email_change_email['to'], sprintf( $email_change_email['subject'], $blog_name ), $email_change_email['message'], $email_change_email['headers'] );
+		}
+
+		if ( $switched_locale ) {
+			restore_previous_locale();
+		}
+	}
+
+	// Update the cookies if the password changed.
+	$current_user = wp_get_current_user();
+	if ( $current_user->ID == $ID ) {
+		if ( isset( $plaintext_pass ) ) {
+			wp_clear_auth_cookie();
+
+			// Here we calculate the expiration length of the current auth cookie and compare it to the default expiration.
+			// If it's greater than this, then we know the user checked 'Remember Me' when they logged in.
+			$logged_in_cookie = wp_parse_auth_cookie( '', 'logged_in' );
+			/** This filter is documented in wp-includes/pluggable.php */
+			$default_cookie_life = apply_filters( 'auth_cookie_expiration', ( 2 * DAY_IN_SECONDS ), $ID, false );
+			$remember            = false;
+			if ( false !== $logged_in_cookie && ( $logged_in_cookie['expiration'] - time() ) > $default_cookie_life ) {
+				$remember = true;
+			}
+
+			wp_set_auth_cookie( $ID, $remember );
+		}
+	}
+
+	return $user_id;
+}
+
+/**
+ * A simpler way of inserting a user into the database.
+ *
+ * Creates a new user with just the username, password, and email. For more
+ * complex user creation use wp_insert_user() to specify more information.
+ *
+ * @since 2.0.0
+ * @see wp_insert_user() More complete way to create a new user
+ *
+ * @param string $username The user's username.
+ * @param string $password The user's password.
+ * @param string $email    Optional. The user's email. Default empty.
+ * @return int|WP_Error The newly created user's ID or a WP_Error object if the user could not
+ *                      be created.
+ */
+function wp_create_user( $username, $password, $email = '' ) {
+	$user_login = wp_slash( $username );
+	$user_email = wp_slash( $email );
+	$user_pass  = $password;
+
+	$userdata = compact( 'user_login', 'user_email', 'user_pass' );
+	return wp_insert_user( $userdata );
+}
+
+/**
+ * Returns a list of meta keys to be (maybe) populated in wp_update_user().
+ *
+ * The list of keys returned via this function are dependent on the presence
+ * of those keys in the user meta data to be set.
+ *
+ * @since 3.3.0
+ * @access private
+ *
+ * @param WP_User $user WP_User instance.
+ * @return array List of user keys to be populated in wp_update_user().
+ */
+function _get_additional_user_keys( $user ) {
+	$keys = array( 'first_name', 'last_name', 'nickname', 'description', 'rich_editing', 'syntax_highlighting', 'comment_shortcuts', 'admin_color', 'use_ssl', 'show_admin_bar_front', 'locale' );
+	return array_merge( $keys, array_keys( wp_get_user_contact_methods( $user ) ) );
+}
+
+/**
+ * Set up the user contact methods.
+ *
+ * Default contact methods were removed in 3.6. A filter dictates contact methods.
+ *
+ * @since 3.7.0
+ *
+ * @param WP_User $user Optional. WP_User object.
+ * @return array Array of contact methods and their labels.
+ */
+function wp_get_user_contact_methods( $user = null ) {
+	$methods = array();
+	if ( get_site_option( 'initial_db_version' ) < 23588 ) {
+		$methods = array(
+			'aim'    => __( 'AIM' ),
+			'yim'    => __( 'Yahoo IM' ),
+			'jabber' => __( 'Jabber / Google Talk' ),
+		);
+	}
+
+	/**
+	 * Filters the user contact methods.
+	 *
+	 * @since 2.9.0
+	 *
+	 * @param array   $methods Array of contact methods and their labels.
+	 * @param WP_User $user    WP_User object.
+	 */
+	return apply_filters( 'user_contactmethods', $methods, $user );
+}
+
+/**
+ * The old private function for setting up user contact methods.
+ *
+ * Use wp_get_user_contact_methods() instead.
+ *
+ * @since 2.9.0
+ * @access private
+ *
+ * @param WP_User $user Optional. WP_User object. Default null.
+ * @return array Array of contact methods and their labels.
+ */
+function _wp_get_user_contactmethods( $user = null ) {
+	return wp_get_user_contact_methods( $user );
+}
+
+/**
+ * Gets the text suggesting how to create strong passwords.
+ *
+ * @since 4.1.0
+ *
+ * @return string The password hint text.
+ */
+function wp_get_password_hint() {
+	$hint = __( 'Hint: The password should be at least twelve characters long. To make it stronger, use upper and lower case letters, numbers, and symbols like ! " ? $ % ^ &amp; ).' );
+
+	/**
+	 * Filters the text describing the site's password complexity policy.
+	 *
+	 * @since 4.1.0
+	 *
+	 * @param string $hint The password hint text.
+	 */
+	return apply_filters( 'password_hint', $hint );
+}
+
+/**
+ * Creates, stores, then returns a password reset key for user.
+ *
+ * @since 4.4.0
+ *
+ * @global PasswordHash $wp_hasher Portable PHP password hashing framework.
+ *
+ * @param WP_User $user User to retrieve password reset key for.
+ *
+ * @return string|WP_Error Password reset key on success. WP_Error on error.
+ */
+function get_password_reset_key( $user ) {
+	global $wp_hasher;
+
+	if ( ! ( $user instanceof WP_User ) ) {
+		return new WP_Error( 'invalidcombo', __( '<strong>ERROR</strong>: There is no account with that username or email address.' ) );
+	}
+
+	/**
+	 * Fires before a new password is retrieved.
+	 *
+	 * Use the {@see 'retrieve_password'} hook instead.
+	 *
+	 * @since 1.5.0
+	 * @deprecated 1.5.1 Misspelled. Use 'retrieve_password' hook instead.
+	 *
+	 * @param string $user_login The user login name.
+	 */
+	do_action( 'retreive_password', $user->user_login );
+
+	/**
+	 * Fires before a new password is retrieved.
+	 *
+	 * @since 1.5.1
+	 *
+	 * @param string $user_login The user login name.
+	 */
+	do_action( 'retrieve_password', $user->user_login );
+
+	$allow = true;
+	if ( is_multisite() && is_user_spammy( $user ) ) {
+		$allow = false;
+	}
+
+	/**
+	 * Filters whether to allow a password to be reset.
+	 *
+	 * @since 2.7.0
+	 *
+	 * @param bool $allow         Whether to allow the password to be reset. Default true.
+	 * @param int  $user_data->ID The ID of the user attempting to reset a password.
+	 */
+	$allow = apply_filters( 'allow_password_reset', $allow, $user->ID );
+
+	if ( ! $allow ) {
+		return new WP_Error( 'no_password_reset', __( 'Password reset is not allowed for this user' ) );
+	} elseif ( is_wp_error( $allow ) ) {
+		return $allow;
+	}
+
+	// Generate something random for a password reset key.
+	$key = wp_generate_password( 20, false );
+
+	/**
+	 * Fires when a password reset key is generated.
+	 *
+	 * @since 2.5.0
+	 *
+	 * @param string $user_login The username for the user.
+	 * @param string $key        The generated password reset key.
+	 */
+	do_action( 'retrieve_password_key', $user->user_login, $key );
+
+	// Now insert the key, hashed, into the DB.
+	if ( empty( $wp_hasher ) ) {
+		require_once ABSPATH . WPINC . '/class-phpass.php';
+		$wp_hasher = new PasswordHash( 8, true );
+	}
+
+	$hashed = time() . ':' . $wp_hasher->HashPassword( $key );
+
+	$key_saved = wp_update_user(
+		array(
+			'ID'                  => $user->ID,
+			'user_activation_key' => $hashed,
+		)
+	);
+
+	if ( is_wp_error( $key_saved ) ) {
+		return $key_saved;
+	}
+
+	return $key;
+}
+
+/**
+ * Retrieves a user row based on password reset key and login
+ *
+ * A key is considered 'expired' if it exactly matches the value of the
+ * user_activation_key field, rather than being matched after going through the
+ * hashing process. This field is now hashed; old values are no longer accepted
+ * but have a different WP_Error code so good user feedback can be provided.
+ *
+ * @since 3.1.0
+ *
+ * @global wpdb         $wpdb      WordPress database object for queries.
+ * @global PasswordHash $wp_hasher Portable PHP password hashing framework instance.
+ *
+ * @param string $key       Hash to validate sending user's password.
+ * @param string $login     The user login.
+ * @return WP_User|WP_Error WP_User object on success, WP_Error object for invalid or expired keys.
+ */
+function check_password_reset_key( $key, $login ) {
+	global $wpdb, $wp_hasher;
+
+	$key = preg_replace( '/[^a-z0-9]/i', '', $key );
+
+	if ( empty( $key ) || ! is_string( $key ) ) {
+		return new WP_Error( 'invalid_key', __( 'Invalid key.' ) );
+	}
+
+	if ( empty( $login ) || ! is_string( $login ) ) {
+		return new WP_Error( 'invalid_key', __( 'Invalid key.' ) );
+	}
+
+	$user = get_user_by( 'login', $login );
+
+	if ( ! $user ) {
+		return new WP_Error( 'invalid_key', __( 'Invalid key.' ) );
+	}
+
+	if ( empty( $wp_hasher ) ) {
+		require_once ABSPATH . WPINC . '/class-phpass.php';
+		$wp_hasher = new PasswordHash( 8, true );
+	}
+
+	/**
+	 * Filters the expiration time of password reset keys.
+	 *
+	 * @since 4.3.0
+	 *
+	 * @param int $expiration The expiration time in seconds.
+	 */
+	$expiration_duration = apply_filters( 'password_reset_expiration', DAY_IN_SECONDS );
+
+	if ( false !== strpos( $user->user_activation_key, ':' ) ) {
+		list( $pass_request_time, $pass_key ) = explode( ':', $user->user_activation_key, 2 );
+		$expiration_time                      = $pass_request_time + $expiration_duration;
+	} else {
+		$pass_key        = $user->user_activation_key;
+		$expiration_time = false;
+	}
+
+	if ( ! $pass_key ) {
+		return new WP_Error( 'invalid_key', __( 'Invalid key.' ) );
+	}
+
+	$hash_is_correct = $wp_hasher->CheckPassword( $key, $pass_key );
+
+	if ( $hash_is_correct && $expiration_time && time() < $expiration_time ) {
+		return $user;
+	} elseif ( $hash_is_correct && $expiration_time ) {
+		// Key has an expiration time that's passed
+		return new WP_Error( 'expired_key', __( 'Invalid key.' ) );
+	}
+
+	if ( hash_equals( $user->user_activation_key, $key ) || ( $hash_is_correct && ! $expiration_time ) ) {
+		$return  = new WP_Error( 'expired_key', __( 'Invalid key.' ) );
+		$user_id = $user->ID;
+
+		/**
+		 * Filters the return value of check_password_reset_key() when an
+		 * old-style key is used.
+		 *
+		 * @since 3.7.0 Previously plain-text keys were stored in the database.
+		 * @since 4.3.0 Previously key hashes were stored without an expiration time.
+		 *
+		 * @param WP_Error $return  A WP_Error object denoting an expired key.
+		 *                          Return a WP_User object to validate the key.
+		 * @param int      $user_id The matched user ID.
+		 */
+		return apply_filters( 'password_reset_key_expired', $return, $user_id );
+	}
+
+	return new WP_Error( 'invalid_key', __( 'Invalid key.' ) );
+}
+
+/**
+ * Handles resetting the user's password.
+ *
+ * @since 2.5.0
+ *
+ * @param WP_User $user     The user
+ * @param string $new_pass New password for the user in plaintext
+ */
+function reset_password( $user, $new_pass ) {
+	/**
+	 * Fires before the user's password is reset.
+	 *
+	 * @since 1.5.0
+	 *
+	 * @param object $user     The user.
+	 * @param string $new_pass New user password.
+	 */
+	do_action( 'password_reset', $user, $new_pass );
+
+	wp_set_password( $new_pass, $user->ID );
+	update_user_option( $user->ID, 'default_password_nag', false, true );
+
+	/**
+	 * Fires after the user's password is reset.
+	 *
+	 * @since 4.4.0
+	 *
+	 * @param WP_User $user     The user.
+	 * @param string  $new_pass New user password.
+	 */
+	do_action( 'after_password_reset', $user, $new_pass );
+}
+
+/**
+ * Handles registering a new user.
+ *
+ * @since 2.5.0
+ *
+ * @param string $user_login User's username for logging in
+ * @param string $user_email User's email address to send password and add
+ * @return int|WP_Error Either user's ID or error on failure.
+ */
+function register_new_user( $user_login, $user_email ) {
+	$errors = new WP_Error();
+
+	$sanitized_user_login = sanitize_user( $user_login );
+	/**
+	 * Filters the email address of a user being registered.
+	 *
+	 * @since 2.1.0
+	 *
+	 * @param string $user_email The email address of the new user.
+	 */
+	$user_email = apply_filters( 'user_registration_email', $user_email );
+
+	// Check the username
+	if ( $sanitized_user_login == '' ) {
+		$errors->add( 'empty_username', __( '<strong>ERROR</strong>: Please enter a username.' ) );
+	} elseif ( ! validate_username( $user_login ) ) {
+		$errors->add( 'invalid_username', __( '<strong>ERROR</strong>: This username is invalid because it uses illegal characters. Please enter a valid username.' ) );
+		$sanitized_user_login = '';
+	} elseif ( username_exists( $sanitized_user_login ) ) {
+		$errors->add( 'username_exists', __( '<strong>ERROR</strong>: This username is already registered. Please choose another one.' ) );
+
+	} else {
+		/** This filter is documented in wp-includes/user.php */
+		$illegal_user_logins = (array) apply_filters( 'illegal_user_logins', array() );
+		if ( in_array( strtolower( $sanitized_user_login ), array_map( 'strtolower', $illegal_user_logins ) ) ) {
+			$errors->add( 'invalid_username', __( '<strong>ERROR</strong>: Sorry, that username is not allowed.' ) );
+		}
+	}
+
+	// Check the email address
+	if ( $user_email == '' ) {
+		$errors->add( 'empty_email', __( '<strong>ERROR</strong>: Please type your email address.' ) );
+	} elseif ( ! is_email( $user_email ) ) {
+		$errors->add( 'invalid_email', __( '<strong>ERROR</strong>: The email address isn&#8217;t correct.' ) );
+		$user_email = '';
+	} elseif ( email_exists( $user_email ) ) {
+		$errors->add( 'email_exists', __( '<strong>ERROR</strong>: This email is already registered, please choose another one.' ) );
+	}
+
+	/**
+	 * Fires when submitting registration form data, before the user is created.
+	 *
+	 * @since 2.1.0
+	 *
+	 * @param string   $sanitized_user_login The submitted username after being sanitized.
+	 * @param string   $user_email           The submitted email.
+	 * @param WP_Error $errors               Contains any errors with submitted username and email,
+	 *                                       e.g., an empty field, an invalid username or email,
+	 *                                       or an existing username or email.
+	 */
+	do_action( 'register_post', $sanitized_user_login, $user_email, $errors );
+
+	/**
+	 * Filters the errors encountered when a new user is being registered.
+	 *
+	 * The filtered WP_Error object may, for example, contain errors for an invalid
+	 * or existing username or email address. A WP_Error object should always returned,
+	 * but may or may not contain errors.
+	 *
+	 * If any errors are present in $errors, this will abort the user's registration.
+	 *
+	 * @since 2.1.0
+	 *
+	 * @param WP_Error $errors               A WP_Error object containing any errors encountered
+	 *                                       during registration.
+	 * @param string   $sanitized_user_login User's username after it has been sanitized.
+	 * @param string   $user_email           User's email.
+	 */
+	$errors = apply_filters( 'registration_errors', $errors, $sanitized_user_login, $user_email );
+
+	if ( $errors->has_errors() ) {
+		return $errors;
+	}
+
+	$user_pass = wp_generate_password( 12, false );
+	$user_id   = wp_create_user( $sanitized_user_login, $user_pass, $user_email );
+	if ( ! $user_id || is_wp_error( $user_id ) ) {
+		$errors->add(
+			'registerfail',
+			sprintf(
+				/* translators: %s: Admin email address. */
+				__( '<strong>ERROR</strong>: Couldn&#8217;t register you&hellip; please contact the <a href="mailto:%s">webmaster</a> !' ),
+				get_option( 'admin_email' )
+			)
+		);
+		return $errors;
+	}
+
+	update_user_option( $user_id, 'default_password_nag', true, true ); //Set up the Password change nag.
+
+	/**
+	 * Fires after a new user registration has been recorded.
+	 *
+	 * @since 4.4.0
+	 *
+	 * @param int $user_id ID of the newly registered user.
+	 */
+	do_action( 'register_new_user', $user_id );
+
+	return $user_id;
+}
+
+/**
+ * Initiates email notifications related to the creation of new users.
+ *
+ * Notifications are sent both to the site admin and to the newly created user.
+ *
+ * @since 4.4.0
+ * @since 4.6.0 Converted the `$notify` parameter to accept 'user' for sending
+ *              notifications only to the user created.
+ *
+ * @param int    $user_id ID of the newly created user.
+ * @param string $notify  Optional. Type of notification that should happen. Accepts 'admin'
+ *                        or an empty string (admin only), 'user', or 'both' (admin and user).
+ *                        Default 'both'.
+ */
+function wp_send_new_user_notifications( $user_id, $notify = 'both' ) {
+	wp_new_user_notification( $user_id, null, $notify );
+}
+
+/**
+ * Retrieve the current session token from the logged_in cookie.
+ *
+ * @since 4.0.0
+ *
+ * @return string Token.
+ */
+function wp_get_session_token() {
+	$cookie = wp_parse_auth_cookie( '', 'logged_in' );
+	return ! empty( $cookie['token'] ) ? $cookie['token'] : '';
+}
+
+/**
+ * Retrieve a list of sessions for the current user.
+ *
+ * @since 4.0.0
+ * @return array Array of sessions.
+ */
+function wp_get_all_sessions() {
+	$manager = WP_Session_Tokens::get_instance( get_current_user_id() );
+	return $manager->get_all();
+}
+
+/**
+ * Remove the current session token from the database.
+ *
+ * @since 4.0.0
+ */
+function wp_destroy_current_session() {
+	$token = wp_get_session_token();
+	if ( $token ) {
+		$manager = WP_Session_Tokens::get_instance( get_current_user_id() );
+		$manager->destroy( $token );
+	}
+}
+
+/**
+ * Remove all but the current session token for the current user for the database.
+ *
+ * @since 4.0.0
+ */
+function wp_destroy_other_sessions() {
+	$token = wp_get_session_token();
+	if ( $token ) {
+		$manager = WP_Session_Tokens::get_instance( get_current_user_id() );
+		$manager->destroy_others( $token );
+	}
+}
+
+/**
+ * Remove all session tokens for the current user from the database.
+ *
+ * @since 4.0.0
+ */
+function wp_destroy_all_sessions() {
+	$manager = WP_Session_Tokens::get_instance( get_current_user_id() );
+	$manager->destroy_all();
+}
+
+/**
+ * Get the user IDs of all users with no role on this site.
+ *
+ * @since 4.4.0
+ * @since 4.9.0 The `$site_id` parameter was added to support multisite.
+ *
+ * @param int|null $site_id Optional. The site ID to get users with no role for. Defaults to the current site.
+ * @return array Array of user IDs.
+ */
+function wp_get_users_with_no_role( $site_id = null ) {
+	global $wpdb;
+
+	if ( ! $site_id ) {
+		$site_id = get_current_blog_id();
+	}
+
+	$prefix = $wpdb->get_blog_prefix( $site_id );
+
+	if ( is_multisite() && $site_id != get_current_blog_id() ) {
+		switch_to_blog( $site_id );
+		$role_names = wp_roles()->get_names();
+		restore_current_blog();
+	} else {
+		$role_names = wp_roles()->get_names();
+	}
+
+	$regex = implode( '|', array_keys( $role_names ) );
+	$regex = preg_replace( '/[^a-zA-Z_\|-]/', '', $regex );
+	$users = $wpdb->get_col(
+		$wpdb->prepare(
+			"
+		SELECT user_id
+		FROM $wpdb->usermeta
+		WHERE meta_key = '{$prefix}capabilities'
+		AND meta_value NOT REGEXP %s
+	",
+			$regex
+		)
+	);
+
+	return $users;
+}
+
+/**
+ * Retrieves the current user object.
+ *
+ * Will set the current user, if the current user is not set. The current user
+ * will be set to the logged-in person. If no user is logged-in, then it will
+ * set the current user to 0, which is invalid and won't have any permissions.
+ *
+ * This function is used by the pluggable functions wp_get_current_user() and
+ * get_currentuserinfo(), the latter of which is deprecated but used for backward
+ * compatibility.
+ *
+ * @since 4.5.0
+ * @access private
+ *
+ * @see wp_get_current_user()
+ * @global WP_User $current_user Checks if the current user is set.
+ *
+ * @return WP_User Current WP_User instance.
+ */
+function _wp_get_current_user() {
+	global $current_user;
+
+	if ( ! empty( $current_user ) ) {
+		if ( $current_user instanceof WP_User ) {
+			return $current_user;
+		}
+
+		// Upgrade stdClass to WP_User
+		if ( is_object( $current_user ) && isset( $current_user->ID ) ) {
+			$cur_id       = $current_user->ID;
+			$current_user = null;
+			wp_set_current_user( $cur_id );
+			return $current_user;
+		}
+
+		// $current_user has a junk value. Force to WP_User with ID 0.
+		$current_user = null;
+		wp_set_current_user( 0 );
+		return $current_user;
+	}
+
+	if ( defined( 'XMLRPC_REQUEST' ) && XMLRPC_REQUEST ) {
+		wp_set_current_user( 0 );
+		return $current_user;
+	}
+
+	/**
+	 * Filters the current user.
+	 *
+	 * The default filters use this to determine the current user from the
+	 * request's cookies, if available.
+	 *
+	 * Returning a value of false will effectively short-circuit setting
+	 * the current user.
+	 *
+	 * @since 3.9.0
+	 *
+	 * @param int|bool $user_id User ID if one has been determined, false otherwise.
+	 */
+	$user_id = apply_filters( 'determine_current_user', false );
+	if ( ! $user_id ) {
+		wp_set_current_user( 0 );
+		return $current_user;
+	}
+
+	wp_set_current_user( $user_id );
+
+	return $current_user;
+}
+
+/**
+ * Send a confirmation request email when a change of user email address is attempted.
+ *
+ * @since 3.0.0
+ * @since 4.9.0 This function was moved from wp-admin/includes/ms.php so it's no longer Multisite specific.
+ *
+ * @global WP_Error $errors WP_Error object.
+ */
+function send_confirmation_on_profile_email() {
+	global $errors;
+
+	$current_user = wp_get_current_user();
+	if ( ! is_object( $errors ) ) {
+		$errors = new WP_Error();
+	}
+
+	if ( $current_user->ID != $_POST['user_id'] ) {
+		return false;
+	}
+
+	if ( $current_user->user_email != $_POST['email'] ) {
+		if ( ! is_email( $_POST['email'] ) ) {
+			$errors->add(
+				'user_email',
+				__( '<strong>ERROR</strong>: The email address isn&#8217;t correct.' ),
+				array(
+					'form-field' => 'email',
+				)
+			);
+
+			return;
+		}
+
+		if ( email_exists( $_POST['email'] ) ) {
+			$errors->add(
+				'user_email',
+				__( '<strong>ERROR</strong>: The email address is already used.' ),
+				array(
+					'form-field' => 'email',
+				)
+			);
+			delete_user_meta( $current_user->ID, '_new_email' );
+
+			return;
+		}
+
+		$hash           = md5( $_POST['email'] . time() . wp_rand() );
+		$new_user_email = array(
+			'hash'     => $hash,
+			'newemail' => $_POST['email'],
+		);
+		update_user_meta( $current_user->ID, '_new_email', $new_user_email );
+
+		$sitename = wp_specialchars_decode( get_option( 'blogname' ), ENT_QUOTES );
+
+		/* translators: Do not translate USERNAME, ADMIN_URL, EMAIL, SITENAME, SITEURL: those are placeholders. */
+		$email_text = __(
+			'Howdy ###USERNAME###,
+
+You recently requested to have the email address on your account changed.
+
+If this is correct, please click on the following link to change it:
+###ADMIN_URL###
+
+You can safely ignore and delete this email if you do not want to
+take this action.
+
+This email has been sent to ###EMAIL###
+
+Regards,
+All at ###SITENAME###
+###SITEURL###'
+		);
+
+		/**
+		 * Filters the text of the email sent when a change of user email address is attempted.
+		 *
+		 * The following strings have a special meaning and will get replaced dynamically:
+		 * ###USERNAME###  The current user's username.
+		 * ###ADMIN_URL### The link to click on to confirm the email change.
+		 * ###EMAIL###     The new email.
+		 * ###SITENAME###  The name of the site.
+		 * ###SITEURL###   The URL to the site.
+		 *
+		 * @since MU (3.0.0)
+		 * @since 4.9.0 This filter is no longer Multisite specific.
+		 *
+		 * @param string $email_text     Text in the email.
+		 * @param array  $new_user_email {
+		 *     Data relating to the new user email address.
+		 *
+		 *     @type string $hash     The secure hash used in the confirmation link URL.
+		 *     @type string $newemail The proposed new email address.
+		 * }
+		 */
+		$content = apply_filters( 'new_user_email_content', $email_text, $new_user_email );
+
+		$content = str_replace( '###USERNAME###', $current_user->user_login, $content );
+		$content = str_replace( '###ADMIN_URL###', esc_url( admin_url( 'profile.php?newuseremail=' . $hash ) ), $content );
+		$content = str_replace( '###EMAIL###', $_POST['email'], $content );
+		$content = str_replace( '###SITENAME###', $sitename, $content );
+		$content = str_replace( '###SITEURL###', home_url(), $content );
+
+		/* translators: New email address notification email subject. %s: Site title. */
+		wp_mail( $_POST['email'], sprintf( __( '[%s] Email Change Request' ), $sitename ), $content );
+
+		$_POST['email'] = $current_user->user_email;
+	}
+}
+
+/**
+ * Adds an admin notice alerting the user to check for confirmation request email
+ * after email address change.
+ *
+ * @since 3.0.0
+ * @since 4.9.0 This function was moved from wp-admin/includes/ms.php so it's no longer Multisite specific.
+ *
+ * @global string $pagenow
+ */
+function new_user_email_admin_notice() {
+	global $pagenow;
+
+	if ( 'profile.php' === $pagenow && isset( $_GET['updated'] ) ) {
+		$email = get_user_meta( get_current_user_id(), '_new_email', true );
+		if ( $email ) {
+			/* translators: %s: New email address. */
+			echo '<div class="notice notice-info"><p>' . sprintf( __( 'Your email address has not been updated yet. Please check your inbox at %s for a confirmation email.' ), '<code>' . esc_html( $email['newemail'] ) . '</code>' ) . '</p></div>';
+		}
+	}
+}
+
+/**
+ * Get all user privacy request types.
+ *
+ * @since 4.9.6
+ * @access private
+ *
+ * @return array List of core privacy action types.
+ */
+function _wp_privacy_action_request_types() {
+	return array(
+		'export_personal_data',
+		'remove_personal_data',
+	);
+}
+
+/**
+ * Registers the personal data exporter for users.
+ *
+ * @since 4.9.6
+ *
+ * @param array $exporters  An array of personal data exporters.
+ * @return array An array of personal data exporters.
+ */
+function wp_register_user_personal_data_exporter( $exporters ) {
+	$exporters['wordpress-user'] = array(
+		'exporter_friendly_name' => __( 'WordPress User' ),
+		'callback'               => 'wp_user_personal_data_exporter',
+	);
+
+	return $exporters;
+}
+
+/**
+ * Finds and exports personal data associated with an email address from the user and user_meta table.
+ *
+ * @since 4.9.6
+ *
+ * @param string $email_address  The users email address.
+ * @return array An array of personal data.
+ */
+function wp_user_personal_data_exporter( $email_address ) {
+	$email_address = trim( $email_address );
+
+	$data_to_export = array();
+
+	$user = get_user_by( 'email', $email_address );
+
+	if ( ! $user ) {
+		return array(
+			'data' => array(),
+			'done' => true,
+		);
+	}
+
+	$user_meta = get_user_meta( $user->ID );
+
+	$user_prop_to_export = array(
+		'ID'              => __( 'User ID' ),
+		'user_login'      => __( 'User Login Name' ),
+		'user_nicename'   => __( 'User Nice Name' ),
+		'user_email'      => __( 'User Email' ),
+		'user_url'        => __( 'User URL' ),
+		'user_registered' => __( 'User Registration Date' ),
+		'display_name'    => __( 'User Display Name' ),
+		'nickname'        => __( 'User Nickname' ),
+		'first_name'      => __( 'User First Name' ),
+		'last_name'       => __( 'User Last Name' ),
+		'description'     => __( 'User Description' ),
+	);
+
+	$user_data_to_export = array();
+
+	foreach ( $user_prop_to_export as $key => $name ) {
+		$value = '';
+
+		switch ( $key ) {
+			case 'ID':
+			case 'user_login':
+			case 'user_nicename':
+			case 'user_email':
+			case 'user_url':
+			case 'user_registered':
+			case 'display_name':
+				$value = $user->data->$key;
+				break;
+			case 'nickname':
+			case 'first_name':
+			case 'last_name':
+			case 'description':
+				$value = $user_meta[ $key ][0];
+				break;
+		}
+
+		if ( ! empty( $value ) ) {
+			$user_data_to_export[] = array(
+				'name'  => $name,
+				'value' => $value,
+			);
+		}
+	}
+
+	$data_to_export[] = array(
+		'group_id'          => 'user',
+		'group_label'       => __( 'User' ),
+		'group_description' => __( 'User&#8217;s profile data.' ),
+		'item_id'           => "user-{$user->ID}",
+		'data'              => $user_data_to_export,
+	);
+
+	return array(
+		'data' => $data_to_export,
+		'done' => true,
+	);
+}
+
+/**
+ * Update log when privacy request is confirmed.
+ *
+ * @since 4.9.6
+ * @access private
+ *
+ * @param int $request_id ID of the request.
+ */
+function _wp_privacy_account_request_confirmed( $request_id ) {
+	$request = wp_get_user_request_data( $request_id );
+
+	if ( ! $request ) {
+		return;
+	}
+
+	if ( ! in_array( $request->status, array( 'request-pending', 'request-failed' ), true ) ) {
+		return;
+	}
+
+	update_post_meta( $request_id, '_wp_user_request_confirmed_timestamp', time() );
+	wp_update_post(
+		array(
+			'ID'          => $request_id,
+			'post_status' => 'request-confirmed',
+		)
+	);
+}
+
+/**
+ * Notify the site administrator via email when a request is confirmed.
+ *
+ * Without this, the admin would have to manually check the site to see if any
+ * action was needed on their part yet.
+ *
+ * @since 4.9.6
+ *
+ * @param int $request_id The ID of the request.
+ */
+function _wp_privacy_send_request_confirmation_notification( $request_id ) {
+	$request = wp_get_user_request_data( $request_id );
+
+	if ( ! is_a( $request, 'WP_User_Request' ) || 'request-confirmed' !== $request->status ) {
+		return;
+	}
+
+	$already_notified = (bool) get_post_meta( $request_id, '_wp_admin_notified', true );
+
+	if ( $already_notified ) {
+		return;
+	}
+
+	$manage_url         = add_query_arg( 'page', $request->action_name, admin_url( 'tools.php' ) );
+	$action_description = wp_user_request_action_description( $request->action_name );
+
+	/**
+	 * Filters the recipient of the data request confirmation notification.
+	 *
+	 * In a Multisite environment, this will default to the email address of the
+	 * network admin because, by default, single site admins do not have the
+	 * capabilities required to process requests. Some networks may wish to
+	 * delegate those capabilities to a single-site admin, or a dedicated person
+	 * responsible for managing privacy requests.
+	 *
+	 * @since 4.9.6
+	 *
+	 * @param string          $admin_email The email address of the notification recipient.
+	 * @param WP_User_Request $request     The request that is initiating the notification.
+	 */
+	$admin_email = apply_filters( 'user_request_confirmed_email_to', get_site_option( 'admin_email' ), $request );
+
+	$email_data = array(
+		'request'     => $request,
+		'user_email'  => $request->email,
+		'description' => $action_description,
+		'manage_url'  => $manage_url,
+		'sitename'    => wp_specialchars_decode( get_option( 'blogname' ), ENT_QUOTES ),
+		'siteurl'     => home_url(),
+		'admin_email' => $admin_email,
+	);
+
+	/* translators: Do not translate SITENAME, USER_EMAIL, DESCRIPTION, MANAGE_URL, SITEURL; those are placeholders. */
+	$email_text = __(
+		'Howdy,
+
+A user data privacy request has been confirmed on ###SITENAME###:
+
+User: ###USER_EMAIL###
+Request: ###DESCRIPTION###
+
+You can view and manage these data privacy requests here:
+
+###MANAGE_URL###
+
+Regards,
+All at ###SITENAME###
+###SITEURL###'
+	);
+
+	/**
+	 * Filters the body of the user request confirmation email.
+	 *
+	 * The email is sent to an administrator when an user request is confirmed.
+	 * The following strings have a special meaning and will get replaced dynamically:
+	 *
+	 * ###SITENAME###    The name of the site.
+	 * ###USER_EMAIL###  The user email for the request.
+	 * ###DESCRIPTION### Description of the action being performed so the user knows what the email is for.
+	 * ###MANAGE_URL###  The URL to manage requests.
+	 * ###SITEURL###     The URL to the site.
+	 *
+	 * @since 4.9.6
+	 *
+	 * @param string $email_text Text in the email.
+	 * @param array  $email_data {
+	 *     Data relating to the account action email.
+	 *
+	 *     @type WP_User_Request $request     User request object.
+	 *     @type string          $user_email  The email address confirming a request
+	 *     @type string          $description Description of the action being performed so the user knows what the email is for.
+	 *     @type string          $manage_url  The link to click manage privacy requests of this type.
+	 *     @type string          $sitename    The site name sending the mail.
+	 *     @type string          $siteurl     The site URL sending the mail.
+	 *     @type string          $admin_email The administrator email receiving the mail.
+	 * }
+	 */
+	$content = apply_filters( 'user_confirmed_action_email_content', $email_text, $email_data );
+
+	$content = str_replace( '###SITENAME###', $email_data['sitename'], $content );
+	$content = str_replace( '###USER_EMAIL###', $email_data['user_email'], $content );
+	$content = str_replace( '###DESCRIPTION###', $email_data['description'], $content );
+	$content = str_replace( '###MANAGE_URL###', esc_url_raw( $email_data['manage_url'] ), $content );
+	$content = str_replace( '###SITEURL###', esc_url_raw( $email_data['siteurl'] ), $content );
+
+	$subject = sprintf(
+		/* translators: Privacy data request confirmed notification email subject. 1: Site title, 2: Name of the confirmed action. */
+		__( '[%1$s] Action Confirmed: %2$s' ),
+		$email_data['sitename'],
+		$action_description
+	);
+
+	/**
+	 * Filters the subject of the user request confirmation email.
+	 *
+	 * @since 4.9.8
+	 *
+	 * @param string $subject    The email subject.
+	 * @param string $sitename   The name of the site.
+	 * @param array  $email_data {
+	 *     Data relating to the account action email.
+	 *
+	 *     @type WP_User_Request $request     User request object.
+	 *     @type string          $user_email  The email address confirming a request
+	 *     @type string          $description Description of the action being performed so the user knows what the email is for.
+	 *     @type string          $manage_url  The link to click manage privacy requests of this type.
+	 *     @type string          $sitename    The site name sending the mail.
+	 *     @type string          $siteurl     The site URL sending the mail.
+	 *     @type string          $admin_email The administrator email receiving the mail.
+	 * }
+	 */
+	$subject = apply_filters( 'user_request_confirmed_email_subject', $subject, $email_data['sitename'], $email_data );
+
+	$email_sent = wp_mail( $email_data['admin_email'], $subject, $content );
+
+	if ( $email_sent ) {
+		update_post_meta( $request_id, '_wp_admin_notified', true );
+	}
+}
+
+/**
+ * Notify the user when their erasure request is fulfilled.
+ *
+ * Without this, the user would never know if their data was actually erased.
+ *
+ * @since 4.9.6
+ *
+ * @param int $request_id The privacy request post ID associated with this request.
+ */
+function _wp_privacy_send_erasure_fulfillment_notification( $request_id ) {
+	$request = wp_get_user_request_data( $request_id );
+
+	if ( ! is_a( $request, 'WP_User_Request' ) || 'request-completed' !== $request->status ) {
+		return;
+	}
+
+	$already_notified = (bool) get_post_meta( $request_id, '_wp_user_notified', true );
+
+	if ( $already_notified ) {
+		return;
+	}
+
+	// Localize message content for user; fallback to site default for visitors.
+	if ( ! empty( $request->user_id ) ) {
+		$locale = get_user_locale( $request->user_id );
+	} else {
+		$locale = get_locale();
+	}
+
+	$switched_locale = switch_to_locale( $locale );
+
+	/**
+	 * Filters the recipient of the data erasure fulfillment notification.
+	 *
+	 * @since 4.9.6
+	 *
+	 * @param string          $user_email The email address of the notification recipient.
+	 * @param WP_User_Request $request    The request that is initiating the notification.
+	 */
+	$user_email = apply_filters( 'user_erasure_fulfillment_email_to', $request->email, $request );
+
+	$email_data = array(
+		'request'            => $request,
+		'message_recipient'  => $user_email,
+		'privacy_policy_url' => get_privacy_policy_url(),
+		'sitename'           => wp_specialchars_decode( get_option( 'blogname' ), ENT_QUOTES ),
+		'siteurl'            => home_url(),
+	);
+
+	$subject = sprintf(
+		/* translators: Erasure request fulfilled notification email subject. %s: Site title. */
+		__( '[%s] Erasure Request Fulfilled' ),
+		$email_data['sitename']
+	);
+
+	/**
+	 * Filters the subject of the email sent when an erasure request is completed.
+	 *
+	 * @since 4.9.8
+	 *
+	 * @param string $subject    The email subject.
+	 * @param string $sitename   The name of the site.
+	 * @param array  $email_data {
+	 *     Data relating to the account action email.
+	 *
+	 *     @type WP_User_Request $request            User request object.
+	 *     @type string          $message_recipient  The address that the email will be sent to. Defaults
+	 *                                               to the value of `$request->email`, but can be changed
+	 *                                               by the `user_erasure_fulfillment_email_to` filter.
+	 *     @type string          $privacy_policy_url Privacy policy URL.
+	 *     @type string          $sitename           The site name sending the mail.
+	 *     @type string          $siteurl            The site URL sending the mail.
+	 * }
+	 */
+	$subject = apply_filters( 'user_erasure_complete_email_subject', $subject, $email_data['sitename'], $email_data );
+
+	if ( empty( $email_data['privacy_policy_url'] ) ) {
+		/* translators: Do not translate SITENAME, SITEURL; those are placeholders. */
+		$email_text = __(
+			'Howdy,
+
+Your request to erase your personal data on ###SITENAME### has been completed.
+
+If you have any follow-up questions or concerns, please contact the site administrator.
+
+Regards,
+All at ###SITENAME###
+###SITEURL###'
+		);
+	} else {
+		/* translators: Do not translate SITENAME, SITEURL, PRIVACY_POLICY_URL; those are placeholders. */
+		$email_text = __(
+			'Howdy,
+
+Your request to erase your personal data on ###SITENAME### has been completed.
+
+If you have any follow-up questions or concerns, please contact the site administrator.
+
+For more information, you can also read our privacy policy: ###PRIVACY_POLICY_URL###
+
+Regards,
+All at ###SITENAME###
+###SITEURL###'
+		);
+	}
+
+	/**
+	 * Filters the body of the data erasure fulfillment notification.
+	 *
+	 * The email is sent to a user when a their data erasure request is fulfilled
+	 * by an administrator.
+	 *
+	 * The following strings have a special meaning and will get replaced dynamically:
+	 *
+	 * ###SITENAME###           The name of the site.
+	 * ###PRIVACY_POLICY_URL### Privacy policy page URL.
+	 * ###SITEURL###            The URL to the site.
+	 *
+	 * @since 4.9.6
+	 *
+	 * @param string $email_text Text in the email.
+	 * @param array  $email_data {
+	 *     Data relating to the account action email.
+	 *
+	 *     @type WP_User_Request $request            User request object.
+	 *     @type string          $message_recipient  The address that the email will be sent to. Defaults
+	 *                                               to the value of `$request->email`, but can be changed
+	 *                                               by the `user_erasure_fulfillment_email_to` filter.
+	 *     @type string          $privacy_policy_url Privacy policy URL.
+	 *     @type string          $sitename           The site name sending the mail.
+	 *     @type string          $siteurl            The site URL sending the mail.
+	 * }
+	 */
+	$content = apply_filters( 'user_confirmed_action_email_content', $email_text, $email_data );
+
+	$content = str_replace( '###SITENAME###', $email_data['sitename'], $content );
+	$content = str_replace( '###PRIVACY_POLICY_URL###', $email_data['privacy_policy_url'], $content );
+	$content = str_replace( '###SITEURL###', esc_url_raw( $email_data['siteurl'] ), $content );
+
+	$email_sent = wp_mail( $user_email, $subject, $content );
+
+	if ( $switched_locale ) {
+		restore_previous_locale();
+	}
+
+	if ( $email_sent ) {
+		update_post_meta( $request_id, '_wp_user_notified', true );
+	}
+}
+
+/**
+ * Return request confirmation message HTML.
+ *
+ * @since 4.9.6
+ * @access private
+ *
+ * @param int $request_id The request ID being confirmed.
+ * @return string $message The confirmation message.
+ */
+function _wp_privacy_account_request_confirmed_message( $request_id ) {
+	$request = wp_get_user_request_data( $request_id );
+
+	$message  = '<p class="success">' . __( 'Action has been confirmed.' ) . '</p>';
+	$message .= '<p>' . __( 'The site administrator has been notified and will fulfill your request as soon as possible.' ) . '</p>';
+
+	if ( $request && in_array( $request->action_name, _wp_privacy_action_request_types(), true ) ) {
+		if ( 'export_personal_data' === $request->action_name ) {
+			$message  = '<p class="success">' . __( 'Thanks for confirming your export request.' ) . '</p>';
+			$message .= '<p>' . __( 'The site administrator has been notified. You will receive a link to download your export via email when they fulfill your request.' ) . '</p>';
+		} elseif ( 'remove_personal_data' === $request->action_name ) {
+			$message  = '<p class="success">' . __( 'Thanks for confirming your erasure request.' ) . '</p>';
+			$message .= '<p>' . __( 'The site administrator has been notified. You will receive an email confirmation when they erase your data.' ) . '</p>';
+		}
+	}
+
+	/**
+	 * Filters the message displayed to a user when they confirm a data request.
+	 *
+	 * @since 4.9.6
+	 *
+	 * @param string $message    The message to the user.
+	 * @param int    $request_id The ID of the request being confirmed.
+	 */
+	$message = apply_filters( 'user_request_action_confirmed_message', $message, $request_id );
+
+	return $message;
+}
+
+/**
+ * Create and log a user request to perform a specific action.
+ *
+ * Requests are stored inside a post type named `user_request` since they can apply to both
+ * users on the site, or guests without a user account.
+ *
+ * @since 4.9.6
+ *
+ * @param string $email_address User email address. This can be the address of a registered or non-registered user.
+ * @param string $action_name   Name of the action that is being confirmed. Required.
+ * @param array  $request_data  Misc data you want to send with the verification request and pass to the actions once the request is confirmed.
+ * @return int|WP_Error Returns the request ID if successful, or a WP_Error object on failure.
+ */
+function wp_create_user_request( $email_address = '', $action_name = '', $request_data = array() ) {
+	$email_address = sanitize_email( $email_address );
+	$action_name   = sanitize_key( $action_name );
+
+	if ( ! is_email( $email_address ) ) {
+		return new WP_Error( 'invalid_email', __( 'Invalid email address.' ) );
+	}
+
+	if ( ! $action_name ) {
+		return new WP_Error( 'invalid_action', __( 'Invalid action name.' ) );
+	}
+
+	$user    = get_user_by( 'email', $email_address );
+	$user_id = $user && ! is_wp_error( $user ) ? $user->ID : 0;
+
+	// Check for duplicates.
+	$requests_query = new WP_Query(
+		array(
+			'post_type'     => 'user_request',
+			'post_name__in' => array( $action_name ),  // Action name stored in post_name column.
+			'title'         => $email_address, // Email address stored in post_title column.
+			'post_status'   => array(
+				'request-pending',
+				'request-confirmed',
+			),
+			'fields'        => 'ids',
+		)
+	);
+
+	if ( $requests_query->found_posts ) {
+		return new WP_Error( 'duplicate_request', __( 'An incomplete request for this email address already exists.' ) );
+	}
+
+	$request_id = wp_insert_post(
+		array(
+			'post_author'   => $user_id,
+			'post_name'     => $action_name,
+			'post_title'    => $email_address,
+			'post_content'  => wp_json_encode( $request_data ),
+			'post_status'   => 'request-pending',
+			'post_type'     => 'user_request',
+			'post_date'     => current_time( 'mysql', false ),
+			'post_date_gmt' => current_time( 'mysql', true ),
+		),
+		true
+	);
+
+	return $request_id;
+}
+
+/**
+ * Get action description from the name and return a string.
+ *
+ * @since 4.9.6
+ *
+ * @param string $action_name Action name of the request.
+ * @return string Human readable action name.
+ */
+function wp_user_request_action_description( $action_name ) {
+	switch ( $action_name ) {
+		case 'export_personal_data':
+			$description = __( 'Export Personal Data' );
+			break;
+		case 'remove_personal_data':
+			$description = __( 'Erase Personal Data' );
+			break;
+		default:
+			/* translators: %s: Action name. */
+			$description = sprintf( __( 'Confirm the "%s" action' ), $action_name );
+			break;
+	}
+
+	/**
+	 * Filters the user action description.
+	 *
+	 * @since 4.9.6
+	 *
+	 * @param string $description The default description.
+	 * @param string $action_name The name of the request.
+	 */
+	return apply_filters( 'user_request_action_description', $description, $action_name );
+}
+
+/**
+ * Send a confirmation request email to confirm an action.
+ *
+ * If the request is not already pending, it will be updated.
+ *
+ * @since 4.9.6
+ *
+ * @param string $request_id ID of the request created via wp_create_user_request().
+ * @return bool|WP_Error True on success, `WP_Error` on failure.
+ */
+function wp_send_user_request( $request_id ) {
+	$request_id = absint( $request_id );
+	$request    = wp_get_user_request_data( $request_id );
+
+	if ( ! $request ) {
+		return new WP_Error( 'invalid_request', __( 'Invalid user request.' ) );
+	}
+
+	// Localize message content for user; fallback to site default for visitors.
+	if ( ! empty( $request->user_id ) ) {
+		$locale = get_user_locale( $request->user_id );
+	} else {
+		$locale = get_locale();
+	}
+
+	$switched_locale = switch_to_locale( $locale );
+
+	$email_data = array(
+		'request'     => $request,
+		'email'       => $request->email,
+		'description' => wp_user_request_action_description( $request->action_name ),
+		'confirm_url' => add_query_arg(
+			array(
+				'action'      => 'confirmaction',
+				'request_id'  => $request_id,
+				'confirm_key' => wp_generate_user_request_key( $request_id ),
+			),
+			wp_login_url()
+		),
+		'sitename'    => wp_specialchars_decode( get_option( 'blogname' ), ENT_QUOTES ),
+		'siteurl'     => home_url(),
+	);
+
+	/* translators: Do not translate DESCRIPTION, CONFIRM_URL, SITENAME, SITEURL: those are placeholders. */
+	$email_text = __(
+		'Howdy,
+
+A request has been made to perform the following action on your account:
+
+     ###DESCRIPTION###
+
+To confirm this, please click on the following link:
+###CONFIRM_URL###
+
+You can safely ignore and delete this email if you do not want to
+take this action.
+
+Regards,
+All at ###SITENAME###
+###SITEURL###'
+	);
+
+	/**
+	 * Filters the text of the email sent when an account action is attempted.
+	 *
+	 * The following strings have a special meaning and will get replaced dynamically:
+	 *
+	 * ###DESCRIPTION### Description of the action being performed so the user knows what the email is for.
+	 * ###CONFIRM_URL### The link to click on to confirm the account action.
+	 * ###SITENAME###    The name of the site.
+	 * ###SITEURL###     The URL to the site.
+	 *
+	 * @since 4.9.6
+	 *
+	 * @param string $email_text Text in the email.
+	 * @param array  $email_data {
+	 *     Data relating to the account action email.
+	 *
+	 *     @type WP_User_Request $request     User request object.
+	 *     @type string          $email       The email address this is being sent to.
+	 *     @type string          $description Description of the action being performed so the user knows what the email is for.
+	 *     @type string          $confirm_url The link to click on to confirm the account action.
+	 *     @type string          $sitename    The site name sending the mail.
+	 *     @type string          $siteurl     The site URL sending the mail.
+	 * }
+	 */
+	$content = apply_filters( 'user_request_action_email_content', $email_text, $email_data );
+
+	$content = str_replace( '###DESCRIPTION###', $email_data['description'], $content );
+	$content = str_replace( '###CONFIRM_URL###', esc_url_raw( $email_data['confirm_url'] ), $content );
+	$content = str_replace( '###EMAIL###', $email_data['email'], $content );
+	$content = str_replace( '###SITENAME###', $email_data['sitename'], $content );
+	$content = str_replace( '###SITEURL###', esc_url_raw( $email_data['siteurl'] ), $content );
+
+	/* translators: Confirm privacy data request notification email subject. 1: Site title, 2: Name of the action. */
+	$subject = sprintf( __( '[%1$s] Confirm Action: %2$s' ), $email_data['sitename'], $email_data['description'] );
+
+	/**
+	 * Filters the subject of the email sent when an account action is attempted.
+	 *
+	 * @since 4.9.6
+	 *
+	 * @param string $subject    The email subject.
+	 * @param string $sitename   The name of the site.
+	 * @param array  $email_data {
+	 *     Data relating to the account action email.
+	 *
+	 *     @type WP_User_Request $request     User request object.
+	 *     @type string          $email       The email address this is being sent to.
+	 *     @type string          $description Description of the action being performed so the user knows what the email is for.
+	 *     @type string          $confirm_url The link to click on to confirm the account action.
+	 *     @type string          $sitename    The site name sending the mail.
+	 *     @type string          $siteurl     The site URL sending the mail.
+	 * }
+	 */
+	$subject = apply_filters( 'user_request_action_email_subject', $subject, $email_data['sitename'], $email_data );
+
+	$email_sent = wp_mail( $email_data['email'], $subject, $content );
+
+	if ( $switched_locale ) {
+		restore_previous_locale();
+	}
+
+	if ( ! $email_sent ) {
+		return new WP_Error( 'privacy_email_error', __( 'Unable to send personal data export confirmation email.' ) );
+	}
+
+	return true;
+}
+
+/**
+ * Returns a confirmation key for a user action and stores the hashed version for future comparison.
+ *
+ * @since 4.9.6
+ *
+ * @param int $request_id Request ID.
+ * @return string Confirmation key.
+ */
+function wp_generate_user_request_key( $request_id ) {
+	global $wp_hasher;
+
+	// Generate something random for a confirmation key.
+	$key = wp_generate_password( 20, false );
+
+	// Return the key, hashed.
+	if ( empty( $wp_hasher ) ) {
+		require_once ABSPATH . WPINC . '/class-phpass.php';
+		$wp_hasher = new PasswordHash( 8, true );
+	}
+
+	wp_update_post(
+		array(
+			'ID'            => $request_id,
+			'post_status'   => 'request-pending',
+			'post_password' => $wp_hasher->HashPassword( $key ),
+		)
+	);
+
+	return $key;
+}
+
+/**
+ * Validate a user request by comparing the key with the request's key.
+ *
+ * @since 4.9.6
+ *
+ * @param string $request_id ID of the request being confirmed.
+ * @param string $key        Provided key to validate.
+ * @return bool|WP_Error WP_Error on failure, true on success.
+ */
+function wp_validate_user_request_key( $request_id, $key ) {
+	global $wp_hasher;
+
+	$request_id = absint( $request_id );
+	$request    = wp_get_user_request_data( $request_id );
+
+	if ( ! $request ) {
+		return new WP_Error( 'invalid_request', __( 'Invalid request.' ) );
+	}
+
+	if ( ! in_array( $request->status, array( 'request-pending', 'request-failed' ), true ) ) {
+		return new WP_Error( 'expired_link', __( 'This link has expired.' ) );
+	}
+
+	if ( empty( $key ) ) {
+		return new WP_Error( 'missing_key', __( 'Missing confirm key.' ) );
+	}
+
+	if ( empty( $wp_hasher ) ) {
+		require_once ABSPATH . WPINC . '/class-phpass.php';
+		$wp_hasher = new PasswordHash( 8, true );
+	}
+
+	$key_request_time = $request->modified_timestamp;
+	$saved_key        = $request->confirm_key;
+
+	if ( ! $saved_key ) {
+		return new WP_Error( 'invalid_key', __( 'Invalid key.' ) );
+	}
+
+	if ( ! $key_request_time ) {
+		return new WP_Error( 'invalid_key', __( 'Invalid action.' ) );
+	}
+
+	/**
+	 * Filters the expiration time of confirm keys.
+	 *
+	 * @since 4.9.6
+	 *
+	 * @param int $expiration The expiration time in seconds.
+	 */
+	$expiration_duration = (int) apply_filters( 'user_request_key_expiration', DAY_IN_SECONDS );
+	$expiration_time     = $key_request_time + $expiration_duration;
+
+	if ( ! $wp_hasher->CheckPassword( $key, $saved_key ) ) {
+		return new WP_Error( 'invalid_key', __( 'Invalid key.' ) );
+	}
+
+	if ( ! $expiration_time || time() > $expiration_time ) {
+		return new WP_Error( 'expired_key', __( 'The confirmation email has expired.' ) );
+	}
+
+	return true;
+}
+
+/**
+ * Return data about a user request.
+ *
+ * @since 4.9.6
+ *
+ * @param int $request_id Request ID to get data about.
+ * @return WP_User_Request|false
+ */
+function wp_get_user_request_data( $request_id ) {
+	$request_id = absint( $request_id );
+	$post       = get_post( $request_id );
+
+	if ( ! $post || 'user_request' !== $post->post_type ) {
+		return false;
+	}
+
+	return new WP_User_Request( $post );
+}