load_textdomain( string $domain, string $mofile, string $locale = null ): bool

Description

Compatibility

Present in every tracked release (6.7.7 to 7.1.0), and compiles on PHP 7.4 through 8.6-dev.

Parameters

$domainstring

Text domain. Unique identifier for retrieving translated strings.

$mofilestring

Path to the .mo file.

$localestringoptional

Locale. Default is the current locale.Default: null

Return value

bool

True on success, false on failure.

Performance profile

How much work a call to load_textdomain() does, and what it touches: the algorithmic scaling, the Zend instruction count per call across PHP versions, the hooks it hands control to, and the core code that calls it. Measured from the compiled opcodes, not a stopwatch, so every number is identical on any machine running the same PHP version, and every function in core is ranked by cost.

Cost class

Light

Touches nothing outside its own arguments.

Scaling

Scales with input

The body loops, so the work grows with what you pass in.

Instructions

11–117

Executed per call on PHP 8.5, depending on the branch taken. The body compiles to 126.

Plugin surface

6 hooks

Third-party callbacks on 'pre_load_textdomain', 'override_load_textdomain', 'load_textdomain' run inside this call, and their cost is not bounded by anything here.

Called by

5

5 places in core call this, so the cost is paid more often than your own code shows.

What it touches

• hookthird-party callbacksapply_filters()called directly

Further down the call graph this can also reach query, option, cache, serialize and transient. Those are the worst case, several calls deep and usually down an error path, not what a normal call pays.

What one call costs · 15 distinct outcomes

One number would be a lie: the work depends on which branch runs. These are every distinct cost load_textdomain() can have, taken from its control-flow graph on PHP 8.5.

Hooks and filters fired · 6

6 hooks fire while load_textdomain() runs, in this order:

1. 1
   apply_filters( pre_load_textdomain )filterline 749 (+23 into the body)

   Filters whether to short-circuit loading .mo file.

2. 2
   apply_filters( override_load_textdomain )filterline 769 (+43 into the body)

   Filters whether to override the .mo file loading.

3. 3
   do_action( load_textdomain )actionline 785 (+59 into the body)

   Fires before the MO translation file is loaded.

4. 4
   apply_filters( load_textdomain_mofile )filterline 795 (+69 into the body)

   Filters MO file path for loading translations for a specific text domain.

5. 5
   apply_filters( translation_file_format )filterline 816 (+90 into the body)

   Filters the preferred file format for translation files.

6. 6
   apply_filters( load_translation_file )filterline 843 (+117 into the body)

   Filters the file path for loading translations for the given text domain.

Uses · 5

• apply_filters()Calls the callback functions that have been added to a filter hook.
• do_action()Calls the callback functions that have been added to an action hook.
• determine_locale()Determines the current locale desired for the request.
• WP_Translation_Controller::get_instance()Utility method to retrieve the main instance of the class.
• WP_Translations::__construct()Constructor.

Used by · 5

• WP_REST_Site_Health_Controller::load_admin_textdomain()Loads the admin textdomain for Site Health tests.
• _load_textdomain_just_in_time()Loads plugin and theme text domains just-in-time.
• load_default_textdomain()Loads default translated strings based on locale.
• wp_load_translations_early()Attempts an early load of translations.
• wp_timezone_choice()Gives a nicely-formatted list of timezone strings.

Source code

View on Trac ↗View on GitHub ↗

726function load_textdomain( $domain, $mofile, $locale = null ) {727	/** @var WP_Textdomain_Registry $wp_textdomain_registry */728	global $l10n, $l10n_unloaded, $wp_textdomain_registry;729 730	$l10n_unloaded = (array) $l10n_unloaded;731 732	if ( ! is_string( $domain ) ) {733		return false;734	}735 736	/**737	 * Filters whether to short-circuit loading .mo file.738	 *739	 * Returning a non-null value from the filter will effectively short-circuit740	 * the loading, returning the passed value instead.741	 *742	 * @since 6.3.0743	 *744	 * @param bool|null   $loaded The result of loading a .mo file. Default null.745	 * @param string      $domain Text domain. Unique identifier for retrieving translated strings.746	 * @param string      $mofile Path to the MO file.747	 * @param string|null $locale Locale.748	 */749	$loaded = apply_filters( 'pre_load_textdomain', null, $domain, $mofile, $locale );750	if ( null !== $loaded ) {751		if ( true === $loaded ) {752			unset( $l10n_unloaded[ $domain ] );753		}754 755		return $loaded;756	}757 758	/**759	 * Filters whether to override the .mo file loading.760	 *761	 * @since 2.9.0762	 * @since 6.2.0 Added the `$locale` parameter.763	 *764	 * @param bool        $override Whether to override the .mo file loading. Default false.765	 * @param string      $domain   Text domain. Unique identifier for retrieving translated strings.766	 * @param string      $mofile   Path to the MO file.767	 * @param string|null $locale   Locale.768	 */769	$plugin_override = apply_filters( 'override_load_textdomain', false, $domain, $mofile, $locale );770 771	if ( true === (bool) $plugin_override ) {772		unset( $l10n_unloaded[ $domain ] );773 774		return true;775	}776 777	/**778	 * Fires before the MO translation file is loaded.779	 *780	 * @since 2.9.0781	 *782	 * @param string $domain Text domain. Unique identifier for retrieving translated strings.783	 * @param string $mofile Path to the .mo file.784	 */785	do_action( 'load_textdomain', $domain, $mofile );786 787	/**788	 * Filters MO file path for loading translations for a specific text domain.789	 *790	 * @since 2.9.0791	 *792	 * @param string $mofile Path to the MO file.793	 * @param string $domain Text domain. Unique identifier for retrieving translated strings.794	 */795	$mofile = apply_filters( 'load_textdomain_mofile', $mofile, $domain );796 797	if ( ! $locale ) {798		$locale = determine_locale();799	}800 801	$i18n_controller = WP_Translation_Controller::get_instance();802 803	// Ensures the correct locale is set as the current one, in case it was filtered.804	$i18n_controller->set_locale( $locale );805

Changelog

Introduced in 1.5.0. Unchanged from 6.7.7 through 7.1.0.

1. 6.7.7
2. 6.8.8
3. 6.9.7
4. 7.0.4
5. 7.1.0

Signature, return type and hooks compared across 5 parsed releases.

About this page

Parsed data

Generated from the wordpress-develop 6.8.8 tag, from src/wp-includes/l10n.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.

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