Title: WP_Textdomain_Registry
Published: November 2, 2022
Last modified: April 28, 2025

---

# class WP_Textdomain_Registry {}

## In this article

 * [Methods](https://developer.wordpress.org/reference/classes/wp_textdomain_registry/?output_format=md#methods)
 * [Source](https://developer.wordpress.org/reference/classes/wp_textdomain_registry/?output_format=md#source)
 * [Changelog](https://developer.wordpress.org/reference/classes/wp_textdomain_registry/?output_format=md#changelog)

[ Back to top](https://developer.wordpress.org/reference/classes/wp_textdomain_registry/?output_format=md#wp--skip-link--target)

Core class used for registering text domains.

## 󠀁[Methods](https://developer.wordpress.org/reference/classes/wp_textdomain_registry/?output_format=md#methods)󠁿

| Name | Description | 
| [WP_Textdomain_Registry::get](https://developer.wordpress.org/reference/classes/wp_textdomain_registry/get/) | Returns the languages directory path for a specific domain and locale. | 
| [WP_Textdomain_Registry::get_language_files_from_path](https://developer.wordpress.org/reference/classes/wp_textdomain_registry/get_language_files_from_path/) | Retrieves translation files from the specified path. | 
| [WP_Textdomain_Registry::get_path_from_lang_dir](https://developer.wordpress.org/reference/classes/wp_textdomain_registry/get_path_from_lang_dir/) | Gets the path to the language directory for the current domain and locale. | 
| [WP_Textdomain_Registry::get_paths_for_domain](https://developer.wordpress.org/reference/classes/wp_textdomain_registry/get_paths_for_domain/) | Returns possible language directory paths for a given text domain. | 
| [WP_Textdomain_Registry::has](https://developer.wordpress.org/reference/classes/wp_textdomain_registry/has/) | Determines whether any MO file paths are available for the domain. | 
| [WP_Textdomain_Registry::init](https://developer.wordpress.org/reference/classes/wp_textdomain_registry/init/) | Initializes the registry. | 
| [WP_Textdomain_Registry::invalidate_mo_files_cache](https://developer.wordpress.org/reference/classes/wp_textdomain_registry/invalidate_mo_files_cache/) | Invalidate the cache for .mo files. | 
| [WP_Textdomain_Registry::set](https://developer.wordpress.org/reference/classes/wp_textdomain_registry/set/) | Sets the language directory path for a specific domain and locale. | 
| [WP_Textdomain_Registry::set_cached_mo_files](https://developer.wordpress.org/reference/classes/wp_textdomain_registry/set_cached_mo_files/) | Reads and caches all available MO files from a given directory. | 
| [WP_Textdomain_Registry::set_custom_path](https://developer.wordpress.org/reference/classes/wp_textdomain_registry/set_custom_path/) | Sets the custom path to the plugin’s/theme’s languages directory. |

## 󠀁[Source](https://developer.wordpress.org/reference/classes/wp_textdomain_registry/?output_format=md#source)󠁿

    ```php
    class WP_Textdomain_Registry {
    	/**
    	 * List of domains and all their language directory paths for each locale.
    	 *
    	 * @since 6.1.0
    	 *
    	 * @var array
    	 */
    	protected $all = array();

    	/**
    	 * List of domains and their language directory path for the current (most recent) locale.
    	 *
    	 * @since 6.1.0
    	 *
    	 * @var array
    	 */
    	protected $current = array();

    	/**
    	 * List of domains and their custom language directory paths.
    	 *
    	 * @see load_plugin_textdomain()
    	 * @see load_theme_textdomain()
    	 *
    	 * @since 6.1.0
    	 *
    	 * @var array
    	 */
    	protected $custom_paths = array();

    	/**
    	 * Holds a cached list of available .mo files to improve performance.
    	 *
    	 * @since 6.1.0
    	 * @since 6.5.0 This property is no longer used.
    	 *
    	 * @var array
    	 *
    	 * @deprecated
    	 */
    	protected $cached_mo_files = array();

    	/**
    	 * Holds a cached list of domains with translations to improve performance.
    	 *
    	 * @since 6.2.0
    	 *
    	 * @var string[]
    	 */
    	protected $domains_with_translations = array();

    	/**
    	 * Initializes the registry.
    	 *
    	 * Hooks into the 'upgrader_process_complete' filter
    	 * to invalidate MO files caches.
    	 *
    	 * @since 6.5.0
    	 */
    	public function init() {
    		add_action( 'upgrader_process_complete', array( $this, 'invalidate_mo_files_cache' ), 10, 2 );
    	}

    	/**
    	 * Returns the languages directory path for a specific domain and locale.
    	 *
    	 * @since 6.1.0
    	 *
    	 * @param string $domain Text domain.
    	 * @param string $locale Locale.
    	 *
    	 * @return string|false Languages directory path or false if there is none available.
    	 */
    	public function get( $domain, $locale ) {
    		$path = $this->all[ $domain ][ $locale ] ?? $this->get_path_from_lang_dir( $domain, $locale );

    		/**
    		 * Filters the determined languages directory path for a specific domain and locale.
    		 *
    		 * @since 6.6.0
    		 *
    		 * @param string|false $path   Languages directory path for the given domain and locale.
    		 * @param string       $domain Text domain.
    		 * @param string       $locale Locale.
    		 */
    		return apply_filters( 'lang_dir_for_domain', $path, $domain, $locale );
    	}

    	/**
    	 * Determines whether any MO file paths are available for the domain.
    	 *
    	 * This is the case if a path has been set for the current locale,
    	 * or if there is no information stored yet, in which case
    	 * _load_textdomain_just_in_time() will fetch the information first.
    	 *
    	 * @since 6.1.0
    	 *
    	 * @param string $domain Text domain.
    	 * @return bool Whether any MO file paths are available for the domain.
    	 */
    	public function has( $domain ) {
    		return (
    			isset( $this->current[ $domain ] ) ||
    			empty( $this->all[ $domain ] ) ||
    			in_array( $domain, $this->domains_with_translations, true )
    		);
    	}

    	/**
    	 * Sets the language directory path for a specific domain and locale.
    	 *
    	 * Also sets the 'current' property for direct access
    	 * to the path for the current (most recent) locale.
    	 *
    	 * @since 6.1.0
    	 *
    	 * @param string       $domain Text domain.
    	 * @param string       $locale Locale.
    	 * @param string|false $path   Language directory path or false if there is none available.
    	 */
    	public function set( $domain, $locale, $path ) {
    		$this->all[ $domain ][ $locale ] = $path ? rtrim( $path, '/' ) . '/' : false;
    		$this->current[ $domain ]        = $this->all[ $domain ][ $locale ];
    	}

    	/**
    	 * Sets the custom path to the plugin's/theme's languages directory.
    	 *
    	 * Used by load_plugin_textdomain() and load_theme_textdomain().
    	 *
    	 * @since 6.1.0
    	 *
    	 * @param string $domain Text domain.
    	 * @param string $path   Language directory path.
    	 */
    	public function set_custom_path( $domain, $path ) {
    		// If just-in-time loading was triggered before, reset the entry so it can be tried again.

    		if ( isset( $this->all[ $domain ] ) ) {
    			$this->all[ $domain ] = array_filter( $this->all[ $domain ] );
    		}

    		if ( empty( $this->current[ $domain ] ) ) {
    			unset( $this->current[ $domain ] );
    		}

    		$this->custom_paths[ $domain ] = rtrim( $path, '/' );
    	}

    	/**
    	 * Retrieves translation files from the specified path.
    	 *
    	 * Allows early retrieval through the 'pre_get_mo_files_from_path' filter to optimize
    	 * performance, especially in directories with many files.
    	 *
    	 * @since 6.5.0
    	 *
    	 * @param string $path The directory path to search for translation files.
    	 * @return array Array of translation file paths. Can contain .mo and .l10n.php files.
    	 */
    	public function get_language_files_from_path( $path ) {
    		$path = rtrim( $path, '/' ) . '/';

    		/**
    		 * Filters the translation files retrieved from a specified path before the actual lookup.
    		 *
    		 * Returning a non-null value from the filter will effectively short-circuit
    		 * the MO files lookup, returning that value instead.
    		 *
    		 * This can be useful in situations where the directory contains a large number of files
    		 * and the default glob() function becomes expensive in terms of performance.
    		 *
    		 * @since 6.5.0
    		 *
    		 * @param null|array $files List of translation files. Default null.
    		 * @param string     $path  The path from which translation files are being fetched.
    		 */
    		$files = apply_filters( 'pre_get_language_files_from_path', null, $path );

    		if ( null !== $files ) {
    			return $files;
    		}

    		$cache_key = md5( $path );
    		$files     = wp_cache_get( $cache_key, 'translation_files' );

    		if ( false === $files ) {
    			$files = glob( $path . '*.mo' );
    			if ( false === $files ) {
    				$files = array();
    			}

    			$php_files = glob( $path . '*.l10n.php' );
    			if ( is_array( $php_files ) ) {
    				$files = array_merge( $files, $php_files );
    			}

    			wp_cache_set( $cache_key, $files, 'translation_files', HOUR_IN_SECONDS );
    		}

    		return $files;
    	}

    	/**
    	 * Invalidate the cache for .mo files.
    	 *
    	 * This function deletes the cache entries related to .mo files when triggered
    	 * by specific actions, such as the completion of an upgrade process.
    	 *
    	 * @since 6.5.0
    	 *
    	 * @param WP_Upgrader $upgrader   Unused. WP_Upgrader instance. In other contexts this might be a
    	 *                                Theme_Upgrader, Plugin_Upgrader, Core_Upgrade, or Language_Pack_Upgrader instance.
    	 * @param array       $hook_extra {
    	 *     Array of bulk item update data.
    	 *
    	 *     @type string $action       Type of action. Default 'update'.
    	 *     @type string $type         Type of update process. Accepts 'plugin', 'theme', 'translation', or 'core'.
    	 *     @type bool   $bulk         Whether the update process is a bulk update. Default true.
    	 *     @type array  $plugins      Array of the basename paths of the plugins' main files.
    	 *     @type array  $themes       The theme slugs.
    	 *     @type array  $translations {
    	 *         Array of translations update data.
    	 *
    	 *         @type string $language The locale the translation is for.
    	 *         @type string $type     Type of translation. Accepts 'plugin', 'theme', or 'core'.
    	 *         @type string $slug     Text domain the translation is for. The slug of a theme/plugin or
    	 *                                'default' for core translations.
    	 *         @type string $version  The version of a theme, plugin, or core.
    	 *     }
    	 * }
    	 */
    	public function invalidate_mo_files_cache( $upgrader, $hook_extra ) {
    		if (
    			! isset( $hook_extra['type'] ) ||
    			'translation' !== $hook_extra['type'] ||
    			array() === $hook_extra['translations']
    		) {
    			return;
    		}

    		$translation_types = array_unique( wp_list_pluck( $hook_extra['translations'], 'type' ) );

    		foreach ( $translation_types as $type ) {
    			switch ( $type ) {
    				case 'plugin':
    					wp_cache_delete( md5( WP_LANG_DIR . '/plugins/' ), 'translation_files' );
    					break;
    				case 'theme':
    					wp_cache_delete( md5( WP_LANG_DIR . '/themes/' ), 'translation_files' );
    					break;
    				default:
    					wp_cache_delete( md5( WP_LANG_DIR . '/' ), 'translation_files' );
    					break;
    			}
    		}
    	}

    	/**
    	 * Returns possible language directory paths for a given text domain.
    	 *
    	 * @since 6.2.0
    	 *
    	 * @param string $domain Text domain.
    	 * @return string[] Array of language directory paths.
    	 */
    	private function get_paths_for_domain( $domain ) {
    		$locations = array(
    			WP_LANG_DIR . '/plugins',
    			WP_LANG_DIR . '/themes',
    		);

    		if ( isset( $this->custom_paths[ $domain ] ) ) {
    			$locations[] = $this->custom_paths[ $domain ];
    		}

    		return $locations;
    	}

    	/**
    	 * Gets the path to the language directory for the current domain and locale.
    	 *
    	 * Checks the plugins and themes language directories as well as any
    	 * custom directory set via load_plugin_textdomain() or load_theme_textdomain().
    	 *
    	 * @since 6.1.0
    	 *
    	 * @see _get_path_to_translation_from_lang_dir()
    	 *
    	 * @param string $domain Text domain.
    	 * @param string $locale Locale.
    	 * @return string|false Language directory path or false if there is none available.
    	 */
    	private function get_path_from_lang_dir( $domain, $locale ) {
    		$locations = $this->get_paths_for_domain( $domain );

    		$found_location = false;

    		foreach ( $locations as $location ) {
    			$files = $this->get_language_files_from_path( $location );

    			$mo_path  = "$location/$domain-$locale.mo";
    			$php_path = "$location/$domain-$locale.l10n.php";

    			foreach ( $files as $file_path ) {
    				if (
    					! in_array( $domain, $this->domains_with_translations, true ) &&
    					str_starts_with( str_replace( "$location/", '', $file_path ), "$domain-" )
    				) {
    					$this->domains_with_translations[] = $domain;
    				}

    				if ( $file_path === $mo_path || $file_path === $php_path ) {
    					$found_location = rtrim( $location, '/' ) . '/';
    					break 2;
    				}
    			}
    		}

    		if ( $found_location ) {
    			$this->set( $domain, $locale, $found_location );

    			return $found_location;
    		}

    		/*
    		 * If no path is found for the given locale and a custom path has been set
    		 * using load_plugin_textdomain/load_theme_textdomain, use that one.
    		 */
    		if ( isset( $this->custom_paths[ $domain ] ) ) {
    			$fallback_location = rtrim( $this->custom_paths[ $domain ], '/' ) . '/';
    			$this->set( $domain, $locale, $fallback_location );
    			return $fallback_location;
    		}

    		$this->set( $domain, $locale, false );

    		return false;
    	}
    }
    ```

[View all references](https://developer.wordpress.org/reference/files/wp-includes/class-wp-textdomain-registry.php/)
[View on Trac](https://core.trac.wordpress.org/browser/tags/6.9.4/src/wp-includes/class-wp-textdomain-registry.php#L19)
[View on GitHub](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/class-wp-textdomain-registry.php#L19-L359)

## 󠀁[Changelog](https://developer.wordpress.org/reference/classes/wp_textdomain_registry/?output_format=md#changelog)󠁿

| Version | Description | 
| [6.1.0](https://developer.wordpress.org/reference/since/6.1.0/) | Introduced. |

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