/wp-admin/includes/plugin.php

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<?php
/**
 * WordPress Plugin Administration API
 *
 * @package WordPress
 * @subpackage Administration
 */

/**
 * Parses the plugin contents to retrieve plugin's metadata.
 *
 * All plugin headers must be on their own line. Plugin description must not have
 * any newlines, otherwise only parts of the description will be displayed.
 * The below is formatted for printing.
 *
 *     /*
 *     Plugin Name: Name of the plugin.
 *     Plugin URI: The home page of the plugin.
 *     Description: Plugin description.
 *     Author: Plugin author's name.
 *     Author URI: Link to the author's website.
 *     Version: Plugin version.
 *     Text Domain: Optional. Unique identifier, should be same as the one used in
 *          load_plugin_textdomain().
 *     Domain Path: Optional. Only useful if the translations are located in a
 *          folder above the plugin's base path. For example, if .mo files are
 *          located in the locale folder then Domain Path will be "/locale/" and
 *          must have the first slash. Defaults to the base folder the plugin is
 *          located in.
 *     Network: Optional. Specify "Network: true" to require that a plugin is activated
 *          across all sites in an installation. This will prevent a plugin from being
 *          activated on a single site when Multisite is enabled.
 *     Requires at least: Optional. Specify the minimum required WordPress version.
 *     Requires PHP: Optional. Specify the minimum required PHP version.
 *     * / # Remove the space to close comment.
 *
 * The first 8 KB of the file will be pulled in and if the plugin data is not
 * within that first 8 KB, then the plugin author should correct their plugin
 * and move the plugin data headers to the top.
 *
 * The plugin file is assumed to have permissions to allow for scripts to read
 * the file. This is not checked however and the file is only opened for
 * reading.
 *
 * @since 1.5.0
 * @since 5.3.0 Added support for `Requires at least` and `Requires PHP` headers.
 *
 * @param string $plugin_file Absolute path to the main plugin file.
 * @param bool   $markup      Optional. If the returned data should have HTML markup applied.
 *                            Default true.
 * @param bool   $translate   Optional. If the returned data should be translated. Default true.
 * @return array {
 *     Plugin data. Values will be empty if not supplied by the plugin.
 *
 *     @type string $Name        Name of the plugin. Should be unique.
 *     @type string $Title       Title of the plugin and link to the plugin's site (if set).
 *     @type string $Description Plugin description.
 *     @type string $Author      Author's name.
 *     @type string $AuthorURI   Author's website address (if set).
 *     @type string $Version     Plugin version.
 *     @type string $TextDomain  Plugin textdomain.
 *     @type string $DomainPath  Plugins relative directory path to .mo files.
 *     @type bool   $Network     Whether the plugin can only be activated network-wide.
 *     @type string $RequiresWP  Minimum required version of WordPress.
 *     @type string $RequiresPHP Minimum required version of PHP.
 * }
 */
function get_plugin_data( $plugin_file, $markup = true, $translate = true ) {

	$default_headers = array(
		'Name'        => 'Plugin Name',
		'PluginURI'   => 'Plugin URI',
		'Version'     => 'Version',
		'Description' => 'Description',
		'Author'      => 'Author',
		'AuthorURI'   => 'Author URI',
		'TextDomain'  => 'Text Domain',
		'DomainPath'  => 'Domain Path',
		'Network'     => 'Network',
		'RequiresWP'  => 'Requires at least',
		'RequiresPHP' => 'Requires PHP',
		// Site Wide Only is deprecated in favor of Network.
		'_sitewide'   => 'Site Wide Only',
	);

	$plugin_data = get_file_data( $plugin_file, $default_headers, 'plugin' );

	// Site Wide Only is the old header for Network.
	if ( ! $plugin_data['Network'] && $plugin_data['_sitewide'] ) {
		/* translators: 1: Site Wide Only: true, 2: Network: true */
		_deprecated_argument( __FUNCTION__, '3.0.0', sprintf( __( 'The %1$s plugin header is deprecated. Use %2$s instead.' ), '<code>Site Wide Only: true</code>', '<code>Network: true</code>' ) );
		$plugin_data['Network'] = $plugin_data['_sitewide'];
	}
	$plugin_data['Network'] = ( 'true' == strtolower( $plugin_data['Network'] ) );
	unset( $plugin_data['_sitewide'] );

	// If no text domain is defined fall back to the plugin slug.
	if ( ! $plugin_data['TextDomain'] ) {
		$plugin_slug = dirname( plugin_basename( $plugin_file ) );
		if ( '.' !== $plugin_slug && false === strpos( $plugin_slug, '/' ) ) {
			$plugin_data['TextDomain'] = $plugin_slug;
		}
	}

	if ( $markup || $translate ) {
		$plugin_data = _get_plugin_data_markup_translate( $plugin_file, $plugin_data, $markup, $translate );
	} else {
		$plugin_data['Title']      = $plugin_data['Name'];
		$plugin_data['AuthorName'] = $plugin_data['Author'];
	}

	return $plugin_data;
}

/**
 * Sanitizes plugin data, optionally adds markup, optionally translates.
 *
 * @since 2.7.0
 *
 * @see get_plugin_data()
 *
 * @access private
 *
 * @param string $plugin_file Path to the main plugin file.
 * @param array  $plugin_data An array of plugin data. See `get_plugin_data()`.
 * @param bool   $markup      Optional. If the returned data should have HTML markup applied.
 *                            Default true.
 * @param bool   $translate   Optional. If the returned data should be translated. Default true.
 * @return array {
 *     Plugin data. Values will be empty if not supplied by the plugin.
 *
 *     @type string $Name        Name of the plugin. Should be unique.
 *     @type string $Title       Title of the plugin and link to the plugin's site (if set).
 *     @type string $Description Plugin description.
 *     @type string $Author      Author's name.
 *     @type string $AuthorURI   Author's website address (if set).
 *     @type string $Version     Plugin version.
 *     @type string $TextDomain  Plugin textdomain.
 *     @type string $DomainPath  Plugins relative directory path to .mo files.
 *     @type bool   $Network     Whether the plugin can only be activated network-wide.
 * }
 */
function _get_plugin_data_markup_translate( $plugin_file, $plugin_data, $markup = true, $translate = true ) {

	// Sanitize the plugin filename to a WP_PLUGIN_DIR relative path.
	$plugin_file = plugin_basename( $plugin_file );

	// Translate fields.
	if ( $translate ) {
		$textdomain = $plugin_data['TextDomain'];
		if ( $textdomain ) {
			if ( ! is_textdomain_loaded( $textdomain ) ) {
				if ( $plugin_data['DomainPath'] ) {
					load_plugin_textdomain( $textdomain, false, dirname( $plugin_file ) . $plugin_data['DomainPath'] );
				} else {
					load_plugin_textdomain( $textdomain, false, dirname( $plugin_file ) );
				}
			}
		} elseif ( 'hello.php' == basename( $plugin_file ) ) {
			$textdomain = 'default';
		}
		if ( $textdomain ) {
			foreach ( array( 'Name', 'PluginURI', 'Description', 'Author', 'AuthorURI', 'Version' ) as $field ) {
				// phpcs:ignore WordPress.WP.I18n.LowLevelTranslationFunction,WordPress.WP.I18n.NonSingularStringLiteralText,WordPress.WP.I18n.NonSingularStringLiteralDomain
				$plugin_data[ $field ] = translate( $plugin_data[ $field ], $textdomain );
			}
		}
	}

	// Sanitize fields.
	$allowed_tags_in_links = array(
		'abbr'    => array( 'title' => true ),
		'acronym' => array( 'title' => true ),
		'code'    => true,
		'em'      => true,
		'strong'  => true,
	);

	$allowed_tags      = $allowed_tags_in_links;
	$allowed_tags['a'] = array(
		'href'  => true,
		'title' => true,
	);

	// Name is marked up inside <a> tags. Don't allow these.
	// Author is too, but some plugins have used <a> here (omitting Author URI).
	$plugin_data['Name']   = wp_kses( $plugin_data['Name'], $allowed_tags_in_links );
	$plugin_data['Author'] = wp_kses( $plugin_data['Author'], $allowed_tags );

	$plugin_data['Description'] = wp_kses( $plugin_data['Description'], $allowed_tags );
	$plugin_data['Version']     = wp_kses( $plugin_data['Version'], $allowed_tags );

	$plugin_data['PluginURI'] = esc_url( $plugin_data['PluginURI'] );
	$plugin_data['AuthorURI'] = esc_url( $plugin_data['AuthorURI'] );

	$plugin_data['Title']      = $plugin_data['Name'];
	$plugin_data['AuthorName'] = $plugin_data['Author'];

	// Apply markup.
	if ( $markup ) {
		if ( $plugin_data['PluginURI'] && $plugin_data['Name'] ) {
			$plugin_data['Title'] = '<a href="' . $plugin_data['PluginURI'] . '">' . $plugin_data['Name'] . '</a>';
		}

		if ( $plugin_data['AuthorURI'] && $plugin_data['Author'] ) {
			$plugin_data['Author'] = '<a href="' . $plugin_data['AuthorURI'] . '">' . $plugin_data['Author'] . '</a>';
		}

		$plugin_data['Description'] = wptexturize( $plugin_data['Description'] );

		if ( $plugin_data['Author'] ) {
			$plugin_data['Description'] .= sprintf(
				/* translators: %s: Plugin author. */
				' <cite>' . __( 'By %s.' ) . '</cite>',
				$plugin_data['Author']
			);
		}
	}

	return $plugin_data;
}

/**
 * Get a list of a plugin's files.
 *
 * @since 2.8.0
 *
 * @param string $plugin Path to the plugin file relative to the plugins directory.
 * @return string[] Array of file names relative to the plugin root.
 */
function get_plugin_files( $plugin ) {
	$plugin_file = WP_PLUGIN_DIR . '/' . $plugin;
	$dir         = dirname( $plugin_file );

	$plugin_files = array( plugin_basename( $plugin_file ) );

	if ( is_dir( $dir ) && WP_PLUGIN_DIR !== $dir ) {

		/**
		 * Filters the array of excluded directories and files while scanning the folder.
		 *
		 * @since 4.9.0
		 *
		 * @param string[] $exclusions Array of excluded directories and files.
		 */
		$exclusions = (array) apply_filters( 'plugin_files_exclusions', array( 'CVS', 'node_modules', 'vendor', 'bower_components' ) );

		$list_files = list_files( $dir, 100, $exclusions );
		$list_files = array_map( 'plugin_basename', $list_files );

		$plugin_files = array_merge( $plugin_files, $list_files );
		$plugin_files = array_values( array_unique( $plugin_files ) );
	}

	return $plugin_files;
}

/**
 * Check the plugins directory and retrieve all plugin files with plugin data.
 *
 * WordPress only supports plugin files in the base plugins directory
 * (wp-content/plugins) and in one directory above the plugins directory
 * (wp-content/plugins/my-plugin). The file it looks for has the plugin data
 * and must be found in those two locations. It is recommended to keep your
 * plugin files in their own directories.
 *
 * The file with the plugin data is the file that will be included and therefore
 * needs to have the main execution for the plugin. This does not mean
 * everything must be contained in the file and it is recommended that the file
 * be split for maintainability. Keep everything in one file for extreme
 * optimization purposes.
 *
 * @since 1.5.0
 *
 * @param string $plugin_folder Optional. Relative path to single plugin folder.
 * @return array[] Array of arrays of plugin data, keyed by plugin file name. See `get_plugin_data()`.
 */
function get_plugins( $plugin_folder = '' ) {

	$cache_plugins = wp_cache_get( 'plugins', 'plugins' );
	if ( ! $cache_plugins ) {
		$cache_plugins = array();
	}

	if ( isset( $cache_plugins[ $plugin_folder ] ) ) {
		return $cache_plugins[ $plugin_folder ];
	}

	$wp_plugins  = array();
	$plugin_root = WP_PLUGIN_DIR;
	if ( ! empty( $plugin_folder ) ) {
		$plugin_root .= $plugin_folder;
	}

	// Files in wp-content/plugins directory.
	$plugins_dir  = @ opendir( $plugin_root );
	$plugin_files = array();
	if ( $plugins_dir ) {
		while ( ( $file = readdir( $plugins_dir ) ) !== false ) {
			if ( substr( $file, 0, 1 ) == '.' ) {
				continue;
			}
			if ( is_dir( $plugin_root . '/' . $file ) ) {
				$plugins_subdir = @ opendir( $plugin_root . '/' . $file );
				if ( $plugins_subdir ) {
					while ( ( $subfile = readdir( $plugins_subdir ) ) !== false ) {
						if ( substr( $subfile, 0, 1 ) == '.' ) {
							continue;
						}
						if ( substr( $subfile, -4 ) == '.php' ) {
							$plugin_files[] = "$file/$subfile";
						}
					}
					closedir( $plugins_subdir );
				}
			} else {
				if ( substr( $file, -4 ) == '.php' ) {
					$plugin_files[] = $file;
				}
			}
		}
		closedir( $plugins_dir );
	}

	if ( empty( $plugin_files ) ) {
		return $wp_plugins;
	}

	foreach ( $plugin_files as $plugin_file ) {
		if ( ! is_readable( "$plugin_root/$plugin_file" ) ) {
			continue;
		}

		// Do not apply markup/translate as it will be cached.
		$plugin_data = get_plugin_data( "$plugin_root/$plugin_file", false, false );

		if ( empty( $plugin_data['Name'] ) ) {
			continue;
		}

		$wp_plugins[ plugin_basename( $plugin_file ) ] = $plugin_data;
	}

	uasort( $wp_plugins, '_sort_uname_callback' );

	$cache_plugins[ $plugin_folder ] = $wp_plugins;
	wp_cache_set( 'plugins', $cache_plugins, 'plugins' );

	return $wp_plugins;
}

/**
 * Check the mu-plugins directory and retrieve all mu-plugin files with any plugin data.
 *
 * WordPress only includes mu-plugin files in the base mu-plugins directory (wp-content/mu-plugins).
 *
 * @since 3.0.0
 * @return array[] Array of arrays of mu-plugin data, keyed by plugin file name. See `get_plugin_data()`.
 */
function get_mu_plugins() {
	$wp_plugins   = array();
	$plugin_files = array();

	if ( ! is_dir( WPMU_PLUGIN_DIR ) ) {
		return $wp_plugins;
	}

	// Files in wp-content/mu-plugins directory.
	$plugins_dir = @opendir( WPMU_PLUGIN_DIR );
	if ( $plugins_dir ) {
		while ( ( $file = readdir( $plugins_dir ) ) !== false ) {
			if ( substr( $file, -4 ) == '.php' ) {
				$plugin_files[] = $file;
			}
		}
	} else {
		return $wp_plugins;
	}

	closedir( $plugins_dir );

	if ( empty( $plugin_files ) ) {
		return $wp_plugins;
	}

	foreach ( $plugin_files as $plugin_file ) {
		if ( ! is_readable( WPMU_PLUGIN_DIR . "/$plugin_file" ) ) {
			continue;
		}

		// Do not apply markup/translate as it will be cached.
		$plugin_data = get_plugin_data( WPMU_PLUGIN_DIR . "/$plugin_file", false, false );

		if ( empty( $plugin_data['Name'] ) ) {
			$plugin_data['Name'] = $plugin_file;
		}

		$wp_plugins[ $plugin_file ] = $plugin_data;
	}

	if ( isset( $wp_plugins['index.php'] ) && filesize( WPMU_PLUGIN_DIR . '/index.php' ) <= 30 ) {
		// Silence is golden.
		unset( $wp_plugins['index.php'] );
	}

	uasort( $wp_plugins, '_sort_uname_callback' );

	return $wp_plugins;
}

/**
 * Callback to sort array by a 'Name' key.
 *
 * @since 3.1.0
 *
 * @access private
 *
 * @param array $a array with 'Name' key.
 * @param array $b array with 'Name' key.
 * @return int Return 0 or 1 based on two string comparison.
 */
function _sort_uname_callback( $a, $b ) {
	return strnatcasecmp( $a['Name'], $b['Name'] );
}

/**
 * Check the wp-content directory and retrieve all drop-ins with any plugin data.
 *
 * @since 3.0.0
 * @return array[] Array of arrays of dropin plugin data, keyed by plugin file name. See `get_plugin_data()`.
 */
function get_dropins() {
	$dropins      = array();
	$plugin_files = array();

	$_dropins = _get_dropins();

	// Files in wp-content directory.
	$plugins_dir = @opendir( WP_CONTENT_DIR );
	if ( $plugins_dir ) {
		while ( ( $file = readdir( $plugins_dir ) ) !== false ) {
			if ( isset( $_dropins[ $file ] ) ) {
				$plugin_files[] = $file;
			}
		}
	} else {
		return $dropins;
	}

	closedir( $plugins_dir );

	if ( empty( $plugin_files ) ) {
		return $dropins;
	}

	foreach ( $plugin_files as $plugin_file ) {
		if ( ! is_readable( WP_CONTENT_DIR . "/$plugin_file" ) ) {
			continue;
		}

		// Do not apply markup/translate as it will be cached.
		$plugin_data = get_plugin_data( WP_CONTENT_DIR . "/$plugin_file", false, false );

		if ( empty( $plugin_data['Name'] ) ) {
			$plugin_data['Name'] = $plugin_file;
		}

		$dropins[ $plugin_file ] = $plugin_data;
	}

	uksort( $dropins, 'strnatcasecmp' );

	return $dropins;
}

/**
 * Returns drop-ins that WordPress uses.
 *
 * Includes Multisite drop-ins only when is_multisite()
 *
 * @since 3.0.0
 * @return array[] Key is file name. The value is an array, with the first value the
 *  purpose of the drop-in and the second value the name of the constant that must be
 *  true for the drop-in to be used, or true if no constant is required.
 */
function _get_dropins() {
	$dropins = array(
		'advanced-cache.php'      => array( __( 'Advanced caching plugin.' ), 'WP_CACHE' ),  // WP_CACHE
		'db.php'                  => array( __( 'Custom database class.' ), true ),          // Auto on load.
		'db-error.php'            => array( __( 'Custom database error message.' ), true ),  // Auto on error.
		'install.php'             => array( __( 'Custom installation script.' ), true ),     // Auto on installation.
		'maintenance.php'         => array( __( 'Custom maintenance message.' ), true ),     // Auto on maintenance.
		'object-cache.php'        => array( __( 'External object cache.' ), true ),          // Auto on load.
		'php-error.php'           => array( __( 'Custom PHP error message.' ), true ),       // Auto on error.
		'fatal-error-handler.php' => array( __( 'Custom PHP fatal error handler.' ), true ), // Auto on error.
	);

	if ( is_multisite() ) {
		$dropins['sunrise.php']        = array( __( 'Executed before Multisite is loaded.' ), 'SUNRISE' ); // SUNRISE
		$dropins['blog-deleted.php']   = array( __( 'Custom site deleted message.' ), true );   // Auto on deleted blog.
		$dropins['blog-inactive.php']  = array( __( 'Custom site inactive message.' ), true );  // Auto on inactive blog.
		$dropins['blog-suspended.php'] = array( __( 'Custom site suspended message.' ), true ); // Auto on archived or spammed blog.
	}

	return $dropins;
}

/**
 * Determines whether a plugin is active.
 *
 * Only plugins installed in the plugins/ folder can be active.
 *
 * Plugins in the mu-plugins/ folder can't be "activated," so this function will
 * return false for those plugins.
 *
 * 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 2.5.0
 *
 * @param string $plugin Path to the plugin file relative to the plugins directory.
 * @return bool True, if in the active plugins list. False, not in the list.
 */
function is_plugin_active( $plugin ) {
	return in_array( $plugin, (array) get_option( 'active_plugins', array() ), true ) || is_plugin_active_for_network( $plugin );
}

/**
 * Determines whether the plugin is inactive.
 *
 * Reverse of is_plugin_active(). Used as a callback.
 *
 * 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 3.1.0
 * @see is_plugin_active()
 *
 * @param string $plugin Path to the plugin file relative to the plugins directory.
 * @return bool True if inactive. False if active.
 */
function is_plugin_inactive( $plugin ) {
	return ! is_plugin_active( $plugin );
}

/**
 * Determines whether the plugin is active for the entire network.
 *
 * Only plugins installed in the plugins/ folder can be active.
 *
 * Plugins in the mu-plugins/ folder can't be "activated," so this function will
 * return false for those plugins.
 *
 * 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 3.0.0
 *
 * @param string $plugin Path to the plugin file relative to the plugins directory.
 * @return bool True if active for the network, otherwise false.
 */
function is_plugin_active_for_network( $plugin ) {
	if ( ! is_multisite() ) {
		return false;
	}

	$plugins = get_site_option( 'active_sitewide_plugins' );
	if ( isset( $plugins[ $plugin ] ) ) {
		return true;
	}

	return false;
}

/**
 * Checks for "Network: true" in the plugin header to see if this should
 * be activated only as a network wide plugin. The plugin would also work
 * when Multisite is not enabled.
 *
 * Checks for "Site Wide Only: true" for backward compatibility.
 *
 * @since 3.0.0
 *
 * @param string $plugin Path to the plugin file relative to the plugins directory.
 * @return bool True if plugin is network only, false otherwise.
 */
function is_network_only_plugin( $plugin ) {
	$plugin_data = get_plugin_data( WP_PLUGIN_DIR . '/' . $plugin );
	if ( $plugin_data ) {
		return $plugin_data['Network'];
	}
	return false;
}

/**
 * Attempts activation of plugin in a "sandbox" and redirects on success.
 *
 * A plugin that is already activated will not attempt to be activated again.
 *
 * The way it works is by setting the redirection to the error before trying to
 * include the plugin file. If the plugin fails, then the redirection will not
 * be overwritten with the success message. Also, the options will not be
 * updated and the activation hook will not be called on plugin error.
 *
 * It should be noted that in no way the below code will actually prevent errors
 * within the file. The code should not be used elsewhere to replicate the
 * "sandbox", which uses redirection to work.
 * {@source 13 1}
 *
 * If any errors are found or text is outputted, then it will be captured to
 * ensure that the success redirection will update the error redirection.
 *
 * @since 2.5.0
 * @since 5.2.0 Test for WordPress version and PHP version compatibility.
 *
 * @param string $plugin       Path to the plugin file relative to the plugins directory.
 * @param string $redirect     Optional. URL to redirect to.
 * @param bool   $network_wide Optional. Whether to enable the plugin for all sites in the network
 *                             or just the current site. Multisite only. Default false.
 * @param bool   $silent       Optional. Whether to prevent calling activation hooks. Default false.
 * @return null|WP_Error Null on success, WP_Error on invalid file.
 */
function activate_plugin( $plugin, $redirect = '', $network_wide = false, $silent = false ) {
	$plugin = plugin_basename( trim( $plugin ) );

	if ( is_multisite() && ( $network_wide || is_network_only_plugin( $plugin ) ) ) {
		$network_wide        = true;
		$current             = get_site_option( 'active_sitewide_plugins', array() );
		$_GET['networkwide'] = 1; // Back compat for plugins looking for this value.
	} else {
		$current = get_option( 'active_plugins', array() );
	}

	$valid = validate_plugin( $plugin );
	if ( is_wp_error( $valid ) ) {
		return $valid;
	}

	$requirements = validate_plugin_requirements( $plugin );
	if ( is_wp_error( $requirements ) ) {
		return $requirements;
	}

	if ( ( $network_wide && ! isset( $current[ $plugin ] ) ) || ( ! $network_wide && ! in_array( $plugin, $current, true ) ) ) {
		if ( ! empty( $redirect ) ) {
			// We'll override this later if the plugin can be included without fatal error.
			wp_redirect( add_query_arg( '_error_nonce', wp_create_nonce( 'plugin-activation-error_' . $plugin ), $redirect ) );
		}

		ob_start();
		wp_register_plugin_realpath( WP_PLUGIN_DIR . '/' . $plugin );
		$_wp_plugin_file = $plugin;
		if ( ! defined( 'WP_SANDBOX_SCRAPING' ) ) {
			define( 'WP_SANDBOX_SCRAPING', true );
		}
		include_once WP_PLUGIN_DIR . '/' . $plugin;
		$plugin = $_wp_plugin_file; // Avoid stomping of the $plugin variable in a plugin.

		if ( ! $silent ) {
			/**
			 * Fires before a plugin is activated.
			 *
			 * If a plugin is silently activated (such as during an update),
			 * this hook does not fire.
			 *
			 * @since 2.9.0
			 *
			 * @param string $plugin       Path to the plugin file relative to the plugins directory.
			 * @param bool   $network_wide Whether to enable the plugin for all sites in the network
			 *                             or just the current site. Multisite only. Default is false.
			 */
			do_action( 'activate_plugin', $plugin, $network_wide );

			/**
			 * Fires as a specific plugin is being activated.
			 *
			 * This hook is the "activation" hook used internally by register_activation_hook().
			 * The dynamic portion of the hook name, `$plugin`, refers to the plugin basename.
			 *
			 * If a plugin is silently activated (such as during an update), this hook does not fire.
			 *
			 * @since 2.0.0
			 *
			 * @param bool $network_wide Whether to enable the plugin for all sites in the network
			 *                           or just the current site. Multisite only. Default is false.
			 */
			do_action( "activate_{$plugin}", $network_wide );
		}

		if ( $network_wide ) {
			$current            = get_site_option( 'active_sitewide_plugins', array() );
			$current[ $plugin ] = time();
			update_site_option( 'active_sitewide_plugins', $current );
		} else {
			$current   = get_option( 'active_plugins', array() );
			$current[] = $plugin;
			sort( $current );
			update_option( 'active_plugins', $current );
		}

		if ( ! $silent ) {
			/**
			 * Fires after a plugin has been activated.
			 *
			 * If a plugin is silently activated (such as during an update),
			 * this hook does not fire.
			 *
			 * @since 2.9.0
			 *
			 * @param string $plugin       Path to the plugin file relative to the plugins directory.
			 * @param bool   $network_wide Whether to enable the plugin for all sites in the network
			 *                             or just the current site. Multisite only. Default is false.
			 */
			do_action( 'activated_plugin', $plugin, $network_wide );
		}

		if ( ob_get_length() > 0 ) {
			$output = ob_get_clean();
			return new WP_Error( 'unexpected_output', __( 'The plugin generated unexpected output.' ), $output );
		}
		ob_end_clean();
	}

	return null;
}

/**
 * Deactivate a single plugin or multiple plugins.
 *
 * The deactivation hook is disabled by the plugin upgrader by using the $silent
 * parameter.
 *
 * @since 2.5.0
 *
 * @param string|string[] $plugins      Single plugin or list of plugins to deactivate.
 * @param bool            $silent       Prevent calling deactivation hooks. Default false.
 * @param bool|null       $network_wide Whether to deactivate the plugin for all sites in the network.
 *                                      A value of null will deactivate plugins for both the network
 *                                      and the current site. Multisite only. Default null.
 */
function deactivate_plugins( $plugins, $silent = false, $network_wide = null ) {
	if ( is_multisite() ) {
		$network_current = get_site_option( 'active_sitewide_plugins', array() );
	}
	$current    = get_option( 'active_plugins', array() );
	$do_blog    = false;
	$do_network = false;

	foreach ( (array) $plugins as $plugin ) {
		$plugin = plugin_basename( trim( $plugin ) );
		if ( ! is_plugin_active( $plugin ) ) {
			continue;
		}

		$network_deactivating = false !== $network_wide && is_plugin_active_for_network( $plugin );

		if ( ! $silent ) {
			/**
			 * Fires before a plugin is deactivated.
			 *
			 * If a plugin is silently deactivated (such as during an update),
			 * this hook does not fire.
			 *
			 * @since 2.9.0
			 *
			 * @param string $plugin               Path to the plugin file relative to the plugins directory.
			 * @param bool   $network_deactivating Whether the plugin is deactivated for all sites in the network
			 *                                     or just the current site. Multisite only. Default false.
			 */
			do_action( 'deactivate_plugin', $plugin, $network_deactivating );
		}

		if ( false !== $network_wide ) {
			if ( is_plugin_active_for_network( $plugin ) ) {
				$do_network = true;
				unset( $network_current[ $plugin ] );
			} elseif ( $network_wide ) {
				continue;
			}
		}

		if ( true !== $network_wide ) {
			$key = array_search( $plugin, $current, true );
			if ( false !== $key ) {
				$do_blog = true;
				unset( $current[ $key ] );
			}
		}

		if ( $do_blog && wp_is_recovery_mode() ) {
			list( $extension ) = explode( '/', $plugin );
			wp_paused_plugins()->delete( $extension );
		}

		if ( ! $silent ) {
			/**
			 * Fires as a specific plugin is being deactivated.
			 *
			 * This hook is the "deactivation" hook used internally by register_deactivation_hook().
			 * The dynamic portion of the hook name, `$plugin`, refers to the plugin basename.
			 *
			 * If a plugin is silently deactivated (such as during an update), this hook does not fire.
			 *
			 * @since 2.0.0
			 *
			 * @param bool $network_deactivating Whether the plugin is deactivated for all sites in the network
			 *                                   or just the current site. Multisite only. Default false.
			 */
			do_action( "deactivate_{$plugin}", $network_deactivating );

			/**
			 * Fires after a plugin is deactivated.
			 *
			 * If a plugin is silently deactivated (such as during an update),
			 * this hook does not fire.
			 *
			 * @since 2.9.0
			 *
			 * @param string $plugin               Path to the plugin file relative to the plugins directory.
			 * @param bool   $network_deactivating Whether the plugin is deactivated for all sites in the network
			 *                                     or just the current site. Multisite only. Default false.
			 */
			do_action( 'deactivated_plugin', $plugin, $network_deactivating );
		}
	}

	if ( $do_blog ) {
		update_option( 'active_plugins', $current );
	}
	if ( $do_network ) {
		update_site_option( 'active_sitewide_plugins', $network_current );
	}
}

/**
 * Activate multiple plugins.
 *
 * When WP_Error is returned, it does not mean that one of the plugins had
 * errors. It means that one or more of the plugin file paths were invalid.
 *
 * The execution will be halted as soon as one of the plugins has an error.
 *
 * @since 2.6.0
 *
 * @param string|string[] $plugins      Single plugin or list of plugins to activate.
 * @param string          $redirect     Redirect to page after successful activation.
 * @param bool            $network_wide Whether to enable the plugin for all sites in the network.
 *                                      Default false.
 * @param bool $silent                  Prevent calling activation hooks. Default false.
 * @return bool|WP_Error True when finished or WP_Error if there were errors during a plugin activation.
 */
function activate_plugins( $plugins, $redirect = '', $network_wide = false, $silent = false ) {
	if ( ! is_array( $plugins ) ) {
		$plugins = array( $plugins );
	}

	$errors = array();
	foreach ( $plugins as $plugin ) {
		if ( ! empty( $redirect ) ) {
			$redirect = add_query_arg( 'plugin', $plugin, $redirect );
		}
		$result = activate_plugin( $plugin, $redirect, $network_wide, $silent );
		if ( is_wp_error( $result ) ) {
			$errors[ $plugin ] = $result;
		}
	}

	if ( ! empty( $errors ) ) {
		return new WP_Error( 'plugins_invalid', __( 'One of the plugins is invalid.' ), $errors );
	}

	return true;
}

/**
 * Remove directory and files of a plugin for a list of plugins.
 *
 * @since 2.6.0
 *
 * @global WP_Filesystem_Base $wp_filesystem WordPress filesystem subclass.
 *
 * @param string[] $plugins    List of plugin paths to delete, relative to the plugins directory.
 * @param string   $deprecated Not used.
 * @return bool|null|WP_Error True on success, false if `$plugins` is empty, `WP_Error` on failure.
 *                            `null` if filesystem credentials are required to proceed.
 */
function delete_plugins( $plugins, $deprecated = '' ) {
	global $wp_filesystem;

	if ( empty( $plugins ) ) {
		return false;
	}

	$checked = array();
	foreach ( $plugins as $plugin ) {
		$checked[] = 'checked[]=' . $plugin;
	}

	$url = wp_nonce_url( 'plugins.php?action=delete-selected&verify-delete=1&' . implode( '&', $checked ), 'bulk-plugins' );

	ob_start();
	$credentials = request_filesystem_credentials( $url );
	$data        = ob_get_clean();

	if ( false === $credentials ) {
		if ( ! empty( $data ) ) {
			require_once ABSPATH . 'wp-admin/admin-header.php';
			echo $data;
			require_once ABSPATH . 'wp-admin/admin-footer.php';
			exit;
		}
		return;
	}

	if ( ! WP_Filesystem( $credentials ) ) {
		ob_start();
		// Failed to connect. Error and request again.
		request_filesystem_credentials( $url, '', true );
		$data = ob_get_clean();

		if ( ! empty( $data ) ) {
			require_once ABSPATH . 'wp-admin/admin-header.php';
			echo $data;
			require_once ABSPATH . 'wp-admin/admin-footer.php';
			exit;
		}
		return;
	}

	if ( ! is_object( $wp_filesystem ) ) {
		return new WP_Error( 'fs_unavailable', __( 'Could not access filesystem.' ) );
	}

	if ( is_wp_error( $wp_filesystem->errors ) && $wp_filesystem->errors->has_errors() ) {
		return new WP_Error( 'fs_error', __( 'Filesystem error.' ), $wp_filesystem->errors );
	}

	// Get the base plugin folder.
	$plugins_dir = $wp_filesystem->wp_plugins_dir();
	if ( empty( $plugins_dir ) ) {
		return new WP_Error( 'fs_no_plugins_dir', __( 'Unable to locate WordPress plugin directory.' ) );
	}

	$plugins_dir = trailingslashit( $plugins_dir );

	$plugin_translations = wp_get_installed_translations( 'plugins' );

	$errors = array();

	foreach ( $plugins as $plugin_file ) {
		// Run Uninstall hook.
		if ( is_uninstallable_plugin( $plugin_file ) ) {
			uninstall_plugin( $plugin_file );
		}

		/**
		 * Fires immediately before a plugin deletion attempt.
		 *
		 * @since 4.4.0
		 *
		 * @param string $plugin_file Path to the plugin file relative to the plugins directory.
		 */
		do_action( 'delete_plugin', $plugin_file );

		$this_plugin_dir = trailingslashit( dirname( $plugins_dir . $plugin_file ) );

		// If plugin is in its own directory, recursively delete the directory.
		// Base check on if plugin includes directory separator AND that it's not the root plugin folder.
		if ( strpos( $plugin_file, '/' ) && $this_plugin_dir != $plugins_dir ) {
			$deleted = $wp_filesystem->delete( $this_plugin_dir, true );
		} else {
			$deleted = $wp_filesystem->delete( $plugins_dir . $plugin_file );
		}

		/**
		 * Fires immediately after a plugin deletion attempt.
		 *
		 * @since 4.4.0
		 *
		 * @param string $plugin_file Path to the plugin file relative to the plugins directory.
		 * @param bool   $deleted     Whether the plugin deletion was successful.
		 */
		do_action( 'deleted_plugin', $plugin_file, $deleted );

		if ( ! $deleted ) {
			$errors[] = $plugin_file;
			continue;
		}

		// Remove language files, silently.
		$plugin_slug = dirname( $plugin_file );
		if ( '.' !== $plugin_slug && ! empty( $plugin_translations[ $plugin_slug ] ) ) {
			$translations = $plugin_translations[ $plugin_slug ];

			foreach ( $translations as $translation => $data ) {
				$wp_filesystem->delete( WP_LANG_DIR . '/plugins/' . $plugin_slug . '-' . $translation . '.po' );
				$wp_filesystem->delete( WP_LANG_DIR . '/plugins/' . $plugin_slug . '-' . $translation . '.mo' );

				$json_translation_files = glob( WP_LANG_DIR . '/plugins/' . $plugin_slug . '-' . $translation . '-*.json' );
				if ( $json_translation_files ) {
					array_map( array( $wp_filesystem, 'delete' ), $json_translation_files );
				}
			}
		}
	}

	// Remove deleted plugins from the plugin updates list.
	$current = get_site_transient( 'update_plugins' );
	if ( $current ) {
		// Don't remove the plugins that weren't deleted.
		$deleted = array_diff( $plugins, $errors );

		foreach ( $deleted as $plugin_file ) {
			unset( $current->response[ $plugin_file ] );
		}

		set_site_transient( 'update_plugins', $current );
	}

	if ( ! empty( $errors ) ) {
		if ( 1 === count( $errors ) ) {
			/* translators: %s: Plugin filename. */
			$message = __( 'Could not fully remove the plugin %s.' );
		} else {
			/* translators: %s: Comma-separated list of plugin filenames. */
			$message = __( 'Could not fully remove the plugins %s.' );
		}

		return new WP_Error( 'could_not_remove_plugin', sprintf( $message, implode( ', ', $errors ) ) );
	}

	return true;
}

/**
 * Validate active plugins
 *
 * Validate all active plugins, deactivates invalid and
 * returns an array of deactivated ones.
 *
 * @since 2.5.0
 * @return WP_Error[] Array of plugin errors keyed by plugin file name.
 */
function validate_active_plugins() {
	$plugins = get_option( 'active_plugins', array() );
	// Validate vartype: array.
	if ( ! is_array( $plugins ) ) {
		update_option( 'active_plugins', array() );
		$plugins = array();
	}

	if ( is_multisite() && current_user_can( 'manage_network_plugins' ) ) {
		$network_plugins = (array) get_site_option( 'active_sitewide_plugins', array() );
		$plugins         = array_merge( $plugins, array_keys( $network_plugins ) );
	}

	if ( empty( $plugins ) ) {
		return array();
	}

	$invalid = array();

	// Invalid plugins get deactivated.
	foreach ( $plugins as $plugin ) {
		$result = validate_plugin( $plugin );
		if ( is_wp_error( $result ) ) {
			$invalid[ $plugin ] = $result;
			deactivate_plugins( $plugin, true );
		}
	}
	return $invalid;
}

/**
 * Validate the plugin path.
 *
 * Checks that the main plugin file exists and is a valid plugin. See validate_file().
 *
 * @since 2.5.0
 *
 * @param string $plugin Path to the plugin file relative to the plugins directory.
 * @return int|WP_Error 0 on success, WP_Error on failure.
 */
function validate_plugin( $plugin ) {
	if ( validate_file( $plugin ) ) {
		return new WP_Error( 'plugin_invalid', __( 'Invalid plugin path.' ) );
	}
	if ( ! file_exists( WP_PLUGIN_DIR . '/' . $plugin ) ) {
		return new WP_Error( 'plugin_not_found', __( 'Plugin file does not exist.' ) );
	}

	$installed_plugins = get_plugins();
	if ( ! isset( $installed_plugins[ $plugin ] ) ) {
		return new WP_Error( 'no_plugin_header', __( 'The plugin does not have a valid header.' ) );
	}
	return 0;
}

/**
 * Validates the plugin requirements for WordPress version and PHP version.
 *
 * Uses the information from `Requires at least` and `Requires PHP` headers
 * defined in the plugin's main PHP file.
 *
 * If the headers are not present in the plugin's main PHP file,
 * `readme.txt` is also checked as a fallback.
 *
 * @since 5.2.0
 * @since 5.3.0 Added support for reading the headers from the plugin's
 *              main PHP file, with `readme.txt` as a fallback.
 *
 * @param string $plugin Path to the plugin file relative to the plugins directory.
 * @return true|WP_Error True if requirements are met, WP_Error on failure.
 */
function validate_plugin_requirements( $plugin ) {
	$plugin_headers = get_plugin_data( WP_PLUGIN_DIR . '/' . $plugin );

	$requirements = array(
		'requires'     => ! empty( $plugin_headers['RequiresWP'] ) ? $plugin_headers['RequiresWP'] : '',
		'requires_php' => ! empty( $plugin_headers['RequiresPHP'] ) ? $plugin_headers['RequiresPHP'] : '',
	);

	$readme_file = WP_PLUGIN_DIR . '/' . dirname( $plugin ) . '/readme.txt';

	if ( file_exists( $readme_file ) ) {
		$readme_headers = get_file_data(
			$readme_file,
			array(
				'requires'     => 'Requires at least',
				'requires_php' => 'Requires PHP',
			),
			'plugin'
		);

		$requirements = array_merge( $readme_headers, $requirements );
	}

	$compatible_wp  = is_wp_version_compatible( $requirements['requires'] );
	$compatible_php = is_php_version_compatible( $requirements['requires_php'] );

	if ( ! $compatible_wp && ! $compatible_php ) {
		return new WP_Error(
			'plugin_wp_php_incompatible',
			sprintf(
				/* translators: %s: Plugin name. */
				_x( '<strong>Error:</strong> Current WordPress and PHP versions do not meet minimum requirements for %s.', 'plugin' ),
				$plugin_headers['Name']
			)
		);
	} elseif ( ! $compatible_php ) {
		return new WP_Error(
			'plugin_php_incompatible',
			sprintf(
				/* translators: %s: Plugin name. */
				_x( '<strong>Error:</strong> Current PHP version does not meet minimum requirements for %s.', 'plugin' ),
				$plugin_headers['Name']
			)
		);
	} elseif ( ! $compatible_wp ) {
		return new WP_Error(
			'plugin_wp_incompatible',
			sprintf(
				/* translators: %s: Plugin name. */
				_x( '<strong>Error:</strong> Current WordPress version does not meet minimum requirements for %s.', 'plugin' ),
				$plugin_headers['Name']
			)
		);
	}

	return true;
}

/**
 * Whether the plugin can be uninstalled.
 *
 * @since 2.7.0
 *
 * @param string $plugin Path to the plugin file relative to the plugins directory.
 * @return bool Whether plugin can be uninstalled.
 */
function is_uninstallable_plugin( $plugin ) {
	$file = plugin_basename( $plugin );

	$uninstallable_plugins = (array) get_option( 'uninstall_plugins' );
	if ( isset( $uninstallable_plugins[ $file ] ) || file_exists( WP_PLUGIN_DIR . '/' . dirname( $file ) . '/uninstall.php' ) ) {
		return true;
	}

	return false;
}

/**
 * Uninstall a single plugin.
 *
 * Calls the uninstall hook, if it is available.
 *
 * @since 2.7.0
 *
 * @param string $plugin Path to the plugin file relative to the plugins directory.
 * @return true True if a plugin's uninstall.php file has been found and included.
 */
function uninstall_plugin( $plugin ) {
	$file = plugin_basename( $plugin );

	$uninstallable_plugins = (array) get_option( 'uninstall_plugins' );

	/**
	 * Fires in uninstall_plugin() immediately before the plugin is uninstalled.
	 *
	 * @since 4.5.0
	 *
	 * @param string $plugin                Path to the plugin file relative to the plugins directory.
	 * @param array  $uninstallable_plugins Uninstallable plugins.
	 */
	do_action( 'pre_uninstall_plugin', $plugin, $uninstallable_plugins );

	if ( file_exists( WP_PLUGIN_DIR . '/' . dirname( $file ) . '/uninstall.php' ) ) {
		if ( isset( $uninstallable_plugins[ $file ] ) ) {
			unset( $uninstallable_plugins[ $file ] );
			update_option( 'uninstall_plugins', $uninstallable_plugins );
		}
		unset( $uninstallable_plugins );

		define( 'WP_UNINSTALL_PLUGIN', $file );
		wp_register_plugin_realpath( WP_PLUGIN_DIR . '/' . $file );
		include WP_PLUGIN_DIR . '/' . dirname( $file ) . '/uninstall.php';

		return true;
	}

	if ( isset( $uninstallable_plugins[ $file ] ) ) {
		$callable = $uninstallable_plugins[ $file ];
		unset( $uninstallable_plugins[ $file ] );
		update_option( 'uninstall_plugins', $uninstallable_plugins );
		unset( $uninstallable_plugins );

		wp_register_plugin_realpath( WP_PLUGIN_DIR . '/' . $file );
		include WP_PLUGIN_DIR . '/' . $file;

		add_action( "uninstall_{$file}", $callable );

		/**
		 * Fires in uninstall_plugin() once the plugin has been uninstalled.
		 *
		 * The action concatenates the 'uninstall_' prefix with the basename of the
		 * plugin passed to uninstall_plugin() to create a dynamically-named action.
		 *
		 * @since 2.7.0
		 */
		do_action( "uninstall_{$file}" );
	}
}

//
// Menu.
//

/**
 * Add a top-level menu page.
 *
 * This function takes a capability which will be used to determine whether
 * or not a page is included in the menu.
 *
 * The function which is hooked in to handle the output of the page must check
 * that the user has the required capability as well.
 *
 * @since 1.5.0
 *
 * @global array $menu
 * @global array $admin_page_hooks
 * @global array $_registered_pages
 * @global array $_parent_pages
 *
 * @param string   $page_title The text to be displayed in the title tags of the page when the menu is selected.
 * @param string   $menu_title The text to be used for the menu.
 * @param string   $capability The capability required for this menu to be displayed to the user.
 * @param string   $menu_slug  The slug name to refer to this menu by. Should be unique for this menu page and only
 *                             include lowercase alphanumeric, dashes, and underscores characters to be compatible
 *                             with sanitize_key().
 * @param callable $function   The function to be called to output the content for this page.
 * @param string   $icon_url   The URL to the icon to be used for this menu.
 *                             * Pass a base64-encoded SVG using a data URI, which will be colored to match
 *                               the color scheme. This should begin with 'data:image/svg+xml;base64,'.
 *                             * Pass the name of a Dashicons helper class to use a font icon,
 *                               e.g. 'dashicons-chart-pie'.
 *                             * Pass 'none' to leave div.wp-menu-image empty so an icon can be added via CSS.
 * @param int      $position   The position in the menu order this item should appear.
 * @return string The resulting page's hook_suffix.
 */
function add_menu_page( $page_title, $menu_title, $capability, $menu_slug, $function = '', $icon_url = '', $position = null ) {
	global $menu, $admin_page_hooks, $_registered_pages, $_parent_pages;

	$menu_slug = plugin_basename( $menu_slug );

	$admin_page_hooks[ $menu_slug ] = sanitize_title( $menu_title );

	$hookname = get_plugin_page_hookname( $menu_slug, '' );

	if ( ! empty( $function ) && ! empty( $hookname ) && current_user_can( $capability ) ) {
		add_action( $hookname, $function );
	}

	if ( empty( $icon_url ) ) {
		$icon_url   = 'dashicons-admin-generic';
		$icon_class = 'menu-icon-generic ';
	} else {
		$icon_url   = set_url_scheme( $icon_url );
		$icon_class = '';
	}

	$new_menu = array( $menu_title, $capability, $menu_slug, $page_title, 'menu-top ' . $icon_class . $hookname, $hookname, $icon_url );

	if ( null === $position ) {
		$menu[] = $new_menu;
	} elseif ( isset( $menu[ "$position" ] ) ) {
		$position            = $position + substr( base_convert( md5( $menu_slug . $menu_title ), 16, 10 ), -5 ) * 0.00001;
		$menu[ "$position" ] = $new_menu;
	} else {
		$menu[ $position ] = $new_menu;
	}

	$_registered_pages[ $hookname ] = true;

	// No parent as top level.
	$_parent_pages[ $menu_slug ] = false;

	return $hookname;
}

/**
 * Add a submenu page.
 *
 * This function takes a capability which will be used to determine whether
 * or not a page is included in the menu.
 *
 * The function which is hooked in to handle the output of the page must check
 * that the user has the required capability as well.
 *
 * @since 1.5.0
 * @since 5.3.0 Added the `$position` parameter.
 *
 * @global array $submenu
 * @global array $menu
 * @global array $_wp_real_parent_file
 * @global bool  $_wp_submenu_nopriv
 * @global array $_registered_pages
 * @global array $_parent_pages
 *
 * @param string   $parent_slug The slug name for the parent menu (or the file name of a standard
 *                              WordPress admin page).
 * @param string   $page_title  The text to be displayed in the title tags of the page when the menu
 *                              is selected.
 * @param string   $menu_title  The text to be used for the menu.
 * @param string   $capability  The capability required for this menu to be displayed to the user.
 * @param string   $menu_slug   The slug name to refer to this menu by. Should be unique for this menu
 *                              and only include lowercase alphanumeric, dashes, and underscores characters
 *                              to be compatible with sanitize_key().
 * @param callable $function    The function to be called to output the content for this page.
 * @param int      $position    The position in the menu order this item should appear.
 * @return string|false The resulting page's hook_suffix, or false if the user does not have the capability required.
 */
function add_submenu_page( $parent_slug, $page_title, $menu_title, $capability, $menu_slug, $function = '', $position = null ) {
	global $submenu, $menu, $_wp_real_parent_file, $_wp_submenu_nopriv,
		$_registered_pages, $_parent_pages;

	$menu_slug   = plugin_basename( $menu_slug );
	$parent_slug = plugin_basename( $parent_slug );

	if ( isset( $_wp_real_parent_file[ $parent_slug ] ) ) {
		$parent_slug = $_wp_real_parent_file[ $parent_slug ];
	}

	if ( ! current_user_can( $capability ) ) {
		$_wp_submenu_nopriv[ $parent_slug ][ $menu_slug ] = true;
		return false;
	}

	/*
	 * If the parent doesn't already have a submenu, add a link to the parent
	 * as the first item in the submenu. If the submenu file is the same as the
	 * parent file someone is trying to link back to the parent manually. In
	 * this case, don't automatically add a link back to avoid duplication.
	 */
	if ( ! isset( $submenu[ $parent_slug ] ) && $menu_slug != $parent_slug ) {
		foreach ( (array) $menu as $parent_menu ) {
			if ( $parent_menu[2] == $parent_slug && current_user_can( $parent_menu[1] ) ) {
				$submenu[ $parent_slug ][] = array_slice( $parent_menu, 0, 4 );
			}
		}
	}

	$new_sub_menu = array( $menu_title, $capability, $menu_slug, $page_title );
	if ( ! is_int( $position ) ) {
		if ( null !== $position ) {
			_doing_it_wrong(
				__FUNCTION__,
				sprintf(
					/* translators: %s: add_submenu_page() */
					__( 'The seventh parameter passed to %s should be an integer representing menu position.' ),
					'<code>add_submenu_page()</code>'
				),
				'5.3.0'
			);
		}

		$submenu[ $parent_slug ][] = $new_sub_menu;
	} else {
		// Append the submenu if the parent item is not present in the submenu,
		// or if position is equal or higher than the number of items in the array.
		if ( ! isset( $submenu[ $parent_slug ] ) || $position >= count( $submenu[ $parent_slug ] ) ) {
			$submenu[ $parent_slug ][] = $new_sub_menu;
		} else {
			// Test for a negative position.
			$position = max( $position, 0 );
			if ( 0 === $position ) {
				// For negative or `0` positions, prepend the submenu.
				array_unshift( $submenu[ $parent_slug ], $new_sub_menu );
			} else {
				// Grab all of the items before the insertion point.
				$before_items = array_slice( $submenu[ $parent_slug ], 0, $position, true );
				// Grab all of the items after the insertion point.
				$after_items = array_slice( $submenu[ $parent_slug ], $position, null, true );
				// Add the new item.
				$before_items[] = $new_sub_menu;
				// Merge the items.
				$submenu[ $parent_slug ] = array_merge( $before_items, $after_items );
			}
		}
	}
	// Sort the parent array.
	ksort( $submenu[ $parent_slug ] );

	$hookname = get_plugin_page_hookname( $menu_slug, $parent_slug );
	if ( ! empty( $function ) && ! empty( $hookname ) ) {
		add_action( $hookname, $function );
	}

	$_registered_pages[ $hookname ]…

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