Localization

Baseline: main 23.0+.

Language File

• Encoding UTF-8 without BOM.
• Translation file name matches the name of the PHP file it accompanies.
• Folder: .../lang/<lang>/<...> mirrors the structure of the main code.

/local/modules/vendor.module/lib/Application/Service/PostService.php
/local/modules/vendor.module/lib/Application/Service/lang/ru/PostService.php
/local/modules/vendor.module/lib/Application/Service/lang/en/PostService.php

Content:

<?php
$MESS['VENDOR_MODULE_POST_PUBLISHED'] = 'Post #NAME# published';
$MESS['VENDOR_MODULE_POST_EMPTY_TITLE'] = 'Post title is empty';

Prefix rules: <VENDOR>_<MODULE>_<CONTEXT>_<CODE> — a short unique key. Without a prefix, conflicts with other modules are likely.

Loc::getMessage and Loading Phrases

use Bitrix\Main\Localization\Loc;

Loc::loadMessages(__FILE__); // knowing where we are — the kernel will find the translation file

echo Loc::getMessage('VENDOR_MODULE_POST_PUBLISHED', ['#NAME#' => $post->getTitle()]);
echo Loc::getMessage('VENDOR_MODULE_POST_PUBLISHED', ['#NAME#' => 'x'], 'en');

• Signature: Loc::getMessage(string $code, ?array $replace = null, ?string $language = null).
• Substitutions — via #PLACEHOLDER# templates (historical convention). Keys in $replace — with hash marks.
• $language — language ID (ru, en). If not passed — current site language.

Loc::loadMessages(__FILE__) resolves the neighboring lang/<lang>/<same_file>.php from the caller path. Loc::loadLanguageFile($path) loads phrases for an arbitrary PHP file path (when the mapping is not “same name next to __FILE__”).

When Explicit Loading is Needed

For components, component templates, site templates, and Bitrix admin files, the kernel will automatically include neighboring lang/<lang>/<same_file>.php. Manually call Loc::loadMessages(__FILE__) if:

• The file is outside the standard structure (e.g., /local/php_interface/).
• You have your own loader/class — each file must itself include its translations, otherwise lazy loading will break.

Arbitrary File

Loc::loadLanguageFile($_SERVER['DOCUMENT_ROOT'] . '/local/php_interface/custom.php');

Module Default Language

$lang = Loc::getDefaultLang(LANGUAGE_ID); // fallback from language settings: 'ru' → 'ru', 'ua' → 'ru'

Use this when forming language package names if the project language is broader than those supported in the module (ua, kz → "fall back" to ru).

Lazy Loading and BX_MESS_LOG

The kernel loads a language file only upon the first getMessage(...) call from it — the "PHP file ↔ language file" mapping must be strict. If a getMessage('FOO_BAR') call comes from one file while the phrase is defined in another, the kernel will start scanning all files — this slows things down.

Diagnostics: enable in /local/php_interface/init.php:

define('BX_MESS_LOG', $_SERVER['DOCUMENT_ROOT'] . '/var/log/bitrix/mess.log');

The log will contain entries like:

[ru]SOME_MESSAGE: not found for /path/to/file.php
CTranslateUtils::CopyMessage('DEMO_CODE', '/path/a.php', '/path/b.php');

How to fix:

• Copy the phrase to the language file of the module/code where the getMessage call originates.
• Rename the code to something unique if it conflicts with the kernel.
• Move the code to the correct file if it physically ended up in the wrong place.

Do not copy automatically — you might duplicate phrases; investigate the cause.

Regional Settings (Culture)

Date/time/name formats are retrieved from Bitrix\Main\Context\Culture:

$culture = \Bitrix\Main\Context::getCurrent()->getCulture();
$culture->getDateTimeFormat();   // 'DD.MM.YYYY HH:MI:SS'
$culture->getDateFormat();       // 'DD.MM.YYYY'
$culture->getShortTimeFormat();  // 'HH:MI'
$culture->getNameFormat();       // '#LAST_NAME# #NAME# #SECOND_NAME#'
$culture->getNumberDecimals();
$culture->getNumberDecSeparator();
$culture->getNumberThousandsSeparator();

Formatting:

use Bitrix\Main\Type\DateTime;

$date = new DateTime();
echo $date->format($culture->getDateTimeFormat());

// Via classic helpers:
echo \FormatDate($culture->getDateFormat(), $date->getTimestamp());
echo \CurrencyFormat(1234.5, 'RUB');

Language setup: Settings → Product Settings → Language Parameters (date/time/name formats are set per site language). If a component is configured for its own format — it will take precedence.

Setting Phrases in JavaScript

PHP code publishes phrases in BX.message(...):

\Bitrix\Main\Page\Asset::getInstance()->addString(
    '<script>' . \Bitrix\Main\Web\Json::encode([
        'VENDOR_POST_SAVE'   => Loc::getMessage('VENDOR_POST_SAVE'),
        'VENDOR_POST_CANCEL' => Loc::getMessage('VENDOR_POST_CANCEL'),
    ]) . '</script>'
);

Or — more idiomatically — via a JS extension in config.php:

return [
    'js'       => 'script.js',
    'css'      => 'style.css',
    'rel'      => ['main.core'],
    'lang_additional' => [
        'VENDOR_POST_SAVE', 'VENDOR_POST_CANCEL',
    ],
];

BX.message('VENDOR_POST_SAVE');

BX.message({ VENDOR_POST_DYNAMIC: 'Loaded asynchronously' });

const welcome = BX.message('WELCOME_TEXT').replace('#NAME#', userName);

BitrixVue 3

// template
<button>{{ $Bitrix.Loc.getMessage('UI_BUTTON_SAVE') }}</button>

// with replacement + reactivity
{{ $Bitrix.Loc.getMessage('DEMO_COUNTER', { '#COUNTER#': this.counter }) }}

// programmatically
this.$Bitrix.Loc.setMessage({ DEMO_COUNTER: 'Counter: #COUNTER#' });

// optimization for heavy templates — (vueInstance, phrasePrefix, phrases?)
import { BitrixVue } from 'ui.vue3';

computed: {
    localize() { return BitrixVue.getFilteredPhrases(this, 'MYCOMP_'); }
}

translate:index Command

php bitrix/bitrix.php translate:index

Indexes language files so that the Settings → Localization → View Files page works (CSV export/import, package building). Run this after bulk adding new phrases to a module.

Multilingual Modules

• Store phrases in lang/ru/, lang/en/, lang/de/ — in the root of the PHP file that uses them.
• In the module's install/index.php, include translations: Loc::loadMessages(__FILE__).
• Use Loc::getDefaultLang(LANGUAGE_ID) to "fall back" to the module's base language (ru) if kz/ua is missing.
• Publish language names in the system via the Interface Languages form — it cannot be set from .settings.php.

Antipatterns

• Hardcoding strings in services/controllers. Error message texts should be via Loc::getMessage.
• getMessage('CODE') in one file when the phrase is defined in another → scanning all files, slowdown.
• Copying phrases between modules via BX_MESS_LOG without analysis — risk of duplication and confusion.
• Outputting dates via date('d.m.Y') instead of Culture::getDateFormat() — breaks multilingual projects.
• Mixing UTF-8 and CP1251 in lang/ — Bitrix will "re-convert" and you'll get garbled text.
• JS phrases written as strings from PHP without htmlspecialcharsbx for headers going into attributes.

Set default_language in .settings.php for kernel default. BitrixVue 3 localization: skill bitrix-vue.