Translations

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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.

In this article, you'll learn how to use the Translation component in the Symfony Framework. You can read the Translation component documentation to learn even more. Overall, the 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 ("Translations");
  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 app and the fallback locales that will be used if Symfony can't find some translation:

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# config/packages/translation.yaml
framework:
    default_locale: 'en'
    translator:
        fallbacks: ['en']
        # ...

The locale used in translations is the one stored on the request. This is typically set via a _locale attribute on your routes (see How to Work with the User's Locale).

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, XLIFF being the recommended format:

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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>

For information on where these files should be located, see Translations.

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 <Translations in Templates>`.

The Translation Process

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

  • The locale of the current user, which is stored on the request is determined;
  • 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.
  • If the message is located in the catalog, the translation is returned. If not, the translator returns the original message.

Message Format

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

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// ...
$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.

4.2

Support for ICU MessageFormat was introduced in Symfony 4.2. Prior to this, pluralization was managed by the transChoice() method.

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.

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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# updates the French translation file with the missing strings found in templates/
$ php bin/console translation:update --dump-messages --force fr

# updates the English translation file with the missing strings found in AppBundle
$ php bin/console translation:update --dump-messages --force en AppBundle

Note

If you want to see the missing translation strings without actually updating the translation files, remove the --force option from the command above.

Tip

If you need to extract translation strings from other sources, such as controllers, forms and flash messages, consider using the more advanced third-party TranslationBundle.

Translation Resource/File Names and Locations

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

  1. the translations/ directory (at the root of the project);
  2. the src/Resources/<bundle name>/translations/ directory;
  3. the Resources/translations/ directory inside of any bundle.

4.2

Using the src/Resources/<bundle name>/translations/ directory to store translations was deprecated in Symfony 4.2. Use instead the directory defined in the default_path option (which is translations/ by default).

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

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 (e.g. admin, navigation or the default messages) - see The Translation Component;
  • 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, including:

  • xlf: XLIFF file;
  • php: PHP file;
  • yaml: YAML 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 xlf for translations. For more options, see The Translation Component.

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'

Note

You can also store translations in a database, or any other storage by providing a custom class implementing the LoaderInterface interface. See the Built-in Symfony Service Tags tag for more information.

Caution

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

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$ php bin/console cache:clear

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 fr_FR and that you're translating the key Symfony is great. To find the French translation, Symfony actually checks translation resources for several locales:

  1. First, Symfony looks for the translation in a fr_FR translation resource (e.g. messages.fr_FR.xlf);
  2. If it wasn't found, Symfony looks for the translation in a fr translation resource (e.g. messages.fr.xlf);
  3. If the translation still isn't found, Symfony uses the fallbacks configuration parameter, which defaults to en (see Configuration).

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 Framework Configuration Reference (FrameworkBundle).

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.

Learn more

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