Translations

5.1 version

Translations

The term "internationalization" (often abbreviated i18n) refers to the process of abstracting strings and other locale-specific pieces out of your application into a layer where they can be translated and converted based on the user's locale (i.e. language and country). For text, this means wrapping each with a function capable of translating the text (or "message") into the language of the user:

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// text will *always* print out in English
echo 'Hello World';

// text can be translated into the end-user's language or
// default to English
echo $translator->trans('Hello World');

Note

The term locale refers roughly to the user's language and country. It can be any string that your application uses to manage translations and other format differences (e.g. currency format). The ISO 639-1 language code, an underscore (_), then the ISO 3166-1 alpha-2 country code (e.g. fr_FR for French/France) is recommended.

The translation process has several steps:

  1. Enable and configure Symfony's translation service;
  2. Abstract strings (i.e. "messages") by wrapping them in calls to the Translator ("Basic Translation");
  3. Create translation resources/files for each supported locale that translate each message in the application;
  4. Determine, set and manage the user's locale for the request and optionally on the user's entire session.

Installation

First, run this command to install the translator before using it:

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$ composer require symfony/translation

Configuration

The previous command creates an initial config file where you can define the default locale of the application and the directory where the translation files are located:

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    # config/packages/translation.yaml
    framework:
        default_locale: 'en'
        translator:
            default_path: '%kernel.project_dir%/translations'
    
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    <!-- config/packages/translation.xml -->
    <?xml version="1.0" encoding="UTF-8" ?>
    <container xmlns="http://symfony.com/schema/dic/services"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xmlns:framework="http://symfony.com/schema/dic/symfony"
        xsi:schemaLocation="http://symfony.com/schema/dic/services
            https://symfony.com/schema/dic/services/services-1.0.xsd
            http://symfony.com/schema/dic/symfony
            https://symfony.com/schema/dic/symfony/symfony-1.0.xsd">
    
        <framework:config default-locale="en">
            <framework:translator>
                <framework:default-path>'%kernel.project_dir%/translations'</framework:default-path>
                <!-- ... -->
            </framework:translator>
        </framework:config>
    </container>
    
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    // config/packages/translation.php
    $container->loadFromExtension('framework', [
        'default_locale' => 'en',
        'translator' => ['default_path' => '%kernel.project_dir%/translations'],
        // ...
    ]);
    

The locale used in translations is the one stored on the request. This is typically set via a _locale attribute on your routes (see The Locale and the URL).

Basic Translation

Translation of text is done through the translator service (Translator). To translate a block of text (called a message), use the trans() method. Suppose, for example, that you're translating a simple message from inside a controller:

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// ...
use Symfony\Contracts\Translation\TranslatorInterface;

public function index(TranslatorInterface $translator)
{
    $translated = $translator->trans('Symfony is great');

    // ...
}

When this code is executed, Symfony will attempt to translate the message "Symfony is great" based on the locale of the user. For this to work, you need to tell Symfony how to translate the message via a "translation resource", which is usually a file that contains a collection of translations for a given locale. This "dictionary" of translations can be created in several different formats:

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    # translations/messages.fr.yaml
    Symfony is great: J'aime Symfony
    
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    <!-- translations/messages.fr.xlf -->
    <?xml version="1.0"?>
    <xliff version="1.2" xmlns="urn:oasis:names:tc:xliff:document:1.2">
        <file source-language="en" datatype="plaintext" original="file.ext">
            <body>
                <trans-unit id="symfony_is_great">
                    <source>Symfony is great</source>
                    <target>J'aime Symfony</target>
                </trans-unit>
            </body>
        </file>
    </xliff>
    
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    // translations/messages.fr.php
    return [
        'Symfony is great' => "J'aime Symfony",
    ];
    

For information on where these files should be located, see Translation Resource/File Names and Locations.

Now, if the language of the user's locale is French (e.g. fr_FR or fr_BE), the message will be translated into J'aime Symfony. You can also translate the message inside your templates.

Using Real or Keyword Messages

This example illustrates the two different philosophies when creating messages to be translated:

$translator->trans('Symfony is great');

$translator->trans('symfony.great');

In the first method, messages are written in the language of the default locale (English in this case). That message is then used as the "id" when creating translations.

In the second method, messages are actually "keywords" that convey the idea of the message. The keyword message is then used as the "id" for any translations. In this case, translations must be made for the default locale (i.e. to translate symfony.great to Symfony is great).

The second method is handy because the message key won't need to be changed in every translation file if you decide that the message should actually read "Symfony is really great" in the default locale.

The choice of which method to use is entirely up to you, but the "keyword" format is often recommended for multi-language applications, whereas for shared bundles that contain translation resources we recommend the real message, so your application can choose to disable the translator layer and you will see a readable message.

Additionally, the php and yaml file formats support nested ids to avoid repeating yourself if you use keywords instead of real text for your ids:

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    symfony:
        is:
            # id is symfony.is.great
            great: Symfony is great
            # id is symfony.is.amazing
            amazing: Symfony is amazing
        has:
            # id is symfony.has.bundles
            bundles: Symfony has bundles
    user:
        # id is user.login
        login: Login
    
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    [
        'symfony' => [
            'is' => [
                // id is symfony.is.great
                'great'   => 'Symfony is great',
                // id is symfony.is.amazing
                'amazing' => 'Symfony is amazing',
            ],
            'has' => [
                // id is symfony.has.bundles
                'bundles' => 'Symfony has bundles',
            ],
        ],
        'user' => [
            // id is user.login
            'login' => 'Login',
        ],
    ];
    

The Translation Process

To actually translate the message, Symfony uses the following process when using the trans() method:

  1. The locale of the current user, which is stored on the request is determined;
  2. A catalog (e.g. big collection) of translated messages is loaded from translation resources defined for the locale (e.g. fr_FR). Messages from the fallback locale are also loaded and added to the catalog if they don't already exist. The end result is a large "dictionary" of translations. This catalog is cached in production to minimize performance impact.
  3. If the message is located in the catalog, the translation is returned. If not, the translator returns the original message.

Tip

When translating strings that are not in the default domain (messages), you must specify the domain as the third argument of trans():

$translator->trans('Symfony is great', [], 'admin');

Message Format

Sometimes, a message containing a variable needs to be translated:

// ...
$translated = $translator->trans('Hello '.$name);

However, creating a translation for this string is impossible since the translator will try to look up the message including the variable portions (e.g. "Hello Ryan" or "Hello Fabien").

Another complication is when you have translations that may or may not be plural, based on some variable:

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There is one apple.
There are 5 apples.

To manage these situations, Symfony follows the ICU MessageFormat syntax by using PHP's MessageFormatter class. Read more about this in How to Translate Messages using the ICU MessageFormat.

Translations in Templates

Most of the time, translation occurs in templates. Symfony provides native support for both Twig and PHP templates:

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<h1>{% trans %}Symfony is great!{% endtrans %}</h1>

Read Using Translation in Templates for more information about the Twig tags and filters for translation.

Forcing the Translator Locale

When translating a message, the translator uses the specified locale or the fallback locale if necessary. You can also manually specify the locale to use for translation:

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$translator->trans(
    'Symfony is great',
    [],
    'messages',
    'fr_FR'
);

Extracting Translation Contents and Updating Catalogs Automatically

The most time-consuming tasks when translating an application is to extract all the template contents to be translated and to keep all the translation files in sync. Symfony includes a command called translation:update that helps you with these tasks:

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# shows all the messages that should be translated for the French language
$ php bin/console translation:update --dump-messages fr

# updates the French translation files with the missing strings for that locale
$ php bin/console translation:update --force fr

# check out the command help to see its options (prefix, output format, domain, sorting, etc.)
$ php bin/console translation:update --help

The translation:update command looks for missing translations in:

  • Templates stored in the templates/ directory (or any other directory defined in the twig.default_path and twig.paths config options);
  • Any PHP file/class that injects or autowires the translator service and makes calls to the trans() function.

Translation Resource/File Names and Locations

Symfony looks for message files (i.e. translations) in the following default locations:

  • the translations/ directory (at the root of the project);
  • the Resources/translations/ directory inside of any bundle.

The locations are listed here with the highest priority first. That is, you can override the translation messages of a bundle in the first directory.

The override mechanism works at a key level: only the overridden keys need to be listed in a higher priority message file. When a key is not found in a message file, the translator will automatically fall back to the lower priority message files.

The filename of the translation files is also important: each message file must be named according to the following path: domain.locale.loader:

  • domain: An optional way to organize messages into groups. Unless parts of the application are explicitly separated from each other, it is recommended to only use default messages domain;
  • locale: The locale that the translations are for (e.g. en_GB, en, etc);
  • loader: How Symfony should load and parse the file (e.g. xlf, php, yaml, etc).

The loader can be the name of any registered loader. By default, Symfony provides many loaders:

  • .yaml: YAML file
  • .xlf: XLIFF file;
  • .php: Returning a PHP array;
  • .csv: CSV file;
  • .json: JSON file;
  • .ini: INI file;
  • .dat, .res: ICU resource bundle;
  • .mo: Machine object format;
  • .po: Portable object format;
  • .qt: QT Translations XML file;

The choice of which loader to use is entirely up to you and is a matter of taste. The recommended option is to use YAML for simple projects and use XLIFF if you're generating translations with specialized programs or teams.

Caution

Each time you create a new message catalog (or install a bundle that includes a translation catalog), be sure to clear your cache so that Symfony can discover the new translation resources:

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$ php bin/console cache:clear

Note

You can add other directories with the paths option in the configuration:

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    # config/packages/translation.yaml
    framework:
        translator:
            paths:
                - '%kernel.project_dir%/custom/path/to/translations'
    
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    <!-- config/packages/translation.xml -->
    <?xml version="1.0" encoding="UTF-8" ?>
    <container xmlns="http://symfony.com/schema/dic/services"
        xmlns:framework="http://symfony.com/schema/dic/symfony"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-Instance"
        xsi:schemaLocation="http://symfony.com/schema/dic/services
            https://symfony.com/schema/dic/services/services-1.0.xsd
            http://symfony.com/schema/dic/symfony
            https://symfony.com/schema/dic/symfony/symfony-1.0.xsd">
    
        <framework:config>
            <framework:translator>
                <framework:path>%kernel.project_dir%/custom/path/to/translations</framework:path>
            </framework:translator>
        </framework:config>
    </container>
    
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    // config/packages/translation.php
    $container->loadFromExtension('framework', [
        'translator' => [
            'paths' => [
                '%kernel.project_dir%/custom/path/to/translations',
            ],
        ],
    ]);
    

Note

You can also store translations in a database, or any other storage by providing a custom class implementing the LoaderInterface interface. See the translation.loader tag for more information.

Handling the User's Locale

Translating happens based on the user's locale. Read How to Work with the User's Locale to learn more about how to handle it.

Fallback Translation Locales

Imagine that the user's locale is es_AR and that you're translating the key Symfony is great. To find the Spanish translation, Symfony actually checks translation resources for several locales:

  1. First, Symfony looks for the translation in a es_AR (Argentinean Spanish) translation resource (e.g. messages.es_AR.yaml);

  2. If it wasn't found, Symfony looks for the translation in the parent locale, which is automatically defined only for some locales. In this example, the parent locale is es_419 (Latin American Spanish);

  3. If it wasn't found, Symfony looks for the translation in a es (Spanish) translation resource (e.g. messages.es.yaml);

  4. If the translation still isn't found, Symfony uses the fallbacks option, which can be configured as follows:

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      # config/packages/translation.yaml
      framework:
          translator:
              fallbacks: ['en']
              # ...
      
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      <!-- config/packages/translation.xml -->
      <?xml version="1.0" encoding="UTF-8" ?>
      <container xmlns="http://symfony.com/schema/dic/services"
          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          xmlns:framework="http://symfony.com/schema/dic/symfony"
          xsi:schemaLocation="http://symfony.com/schema/dic/services
              https://symfony.com/schema/dic/services/services-1.0.xsd
              http://symfony.com/schema/dic/symfony
              https://symfony.com/schema/dic/symfony/symfony-1.0.xsd">
      
          <framework:config>
              <framework:translator>
                  <framework:fallback>en</framework:fallback>
                  <!-- ... -->
              </framework:translator>
          </framework:config>
      </container>
      
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      // config/packages/translation.php
      $container->loadFromExtension('framework', [
          'translator' => ['fallbacks' => ['en']],
          // ...
      ]);
      

Note

When Symfony can't find a translation in the given locale, it will add the missing translation to the log file. For details, see logging.

Translating Database Content

The translation of database content should be handled by Doctrine through the Translatable Extension or the Translatable Behavior (PHP 5.4+). For more information, see the documentation for these libraries.

Debugging Translations

When you work with many translation messages in different languages, it can be hard to keep track which translations are missing and which are not used anymore. Read How to Find Missing or Unused Translation Messages to find out how to identify these messages.

Summary

With the Symfony Translation component, creating an internationalized application no longer needs to be a painful process and boils down to these steps:

  • Abstract messages in your application by wrapping each in the trans() method;
  • Translate each message into multiple locales by creating translation message files. Symfony discovers and processes each file because its name follows a specific convention;
  • Manage the user's locale, which is stored on the request, but can also be set on the user's session.

This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.