Translations

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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
dump('Hello World');
die();

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

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 ("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.

Configuration

Translations are handled by a translator service that uses the user's locale to lookup and return translated messages. Before using it, enable the translator in your configuration:

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# app/config/config.yml
framework:
    translator: { fallbacks: [en] }

See Translations for details on the fallbacks key and what Symfony does when it doesn't find a translation.

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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// ...

public function indexAction()
{
    $translated = $this->get('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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# messages.fr.yml
Symfony is great: J'aime Symfony

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.

Using Real or Keyword Messages

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

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$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

The Translation Process

To actually translate the message, Symfony uses a simple process:

  1. The locale of the current user, which is stored on the request is determined;
  2. A catalog (i.e. 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.
  3. If the message is located in the catalog, the translation is returned. If not, the translator returns the original message.

When using the trans() method, Symfony looks for the exact string inside the appropriate message catalog and returns it (if it exists).

Tip

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

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

Message Placeholders

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

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public function indexAction($name)
{
    $translated = $this->get('translator')->trans('Hello '.$name.'!');

    // ...
}

However, creating a translation for this string is impossible since the translator will try to look up the exact message, including the variable portions (e.g. "Hello Ryan!" or "Hello Fabien!"). Instead of writing a translation for every possible iteration of the $name variable, you can replace the variable with a "placeholder":

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// ...

public function indexAction($name)
{
    $translated = $this->get('translator')->trans('Hello %name%');

    // ...
}

Symfony will now look for a translation of the raw message (Hello %name%) and then replace the placeholders with their values. Creating a translation is done just as before:

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'Hello %name%!': Bonjour %name% !

Note

The placeholders can take on any form as the full message is reconstructed using the PHP strtr function. But the %...% form is recommended, to avoid problems when using Twig.

As you've seen, creating a translation is a two-step process:

  1. Abstract the message that needs to be translated by processing it through the Translator.
  2. Create a translation for the message in each locale that you choose to support.

The second step is done by creating message catalogs that define the translations for any number of different locales.

Pluralization

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.

When a translation has different forms due to pluralization, you can provide all the forms as a string separated by a pipe (|):

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'There is one apple|There are %count% apples'

To translate these messages, use the transChoice() method or the transchoice tag/filter in your template. To translate pluralized messages, use the transChoice() method:

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// the %count% placeholder is assigned to the second argument...
$this->get('translator')->transChoice(
    'There is one apple|There are %count% apples',
    10
);

// ...but you can define more placeholders if needed
$this->get('translator')->transChoice(
    'Hurry up %name%! There is one apple left.|There are %count% apples left.',
    10,
    // no need to include %count% here; Symfony does that for you
    ['%name%' => $user->getName()]
);

The second argument (10 in this example) is the number of objects being described and is used to determine which translation to use and also to populate the %count% placeholder.

3.2

Before Symfony 3.2, the placeholder used to select the plural (%count% in this example) must be included in the third optional argument of the transChoice() method:

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$translator->transChoice(
    'There is one apple|There are %count% apples',
    10,
    ['%count%' => 10]
);

Starting from Symfony 3.2, when the only placeholder is %count%, you don't have to pass this third argument.

Based on the given number, the translator chooses the right plural form. In English, most words have a singular form when there is exactly one object and a plural form for all other numbers (0, 2, 3...). So, if count is 1, the translator will use the first string (There is one apple) as the translation. Otherwise it will use There are %count% apples.

Here is the French translation:

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'Il y a %count% pomme|Il y a %count% pommes'

Even if the string looks similar (it is made of two sub-strings separated by a pipe), the French rules are different: the first form (no plural) is used when count is 0 or 1. So, the translator will automatically use the first string (Il y a %count% pomme) when count is 0 or 1.

Each locale has its own set of rules, with some having as many as six different plural forms with complex rules behind which numbers map to which plural form. The rules are quite simple for English and French, but for Russian, you'd may want a hint to know which rule matches which string. To help translators, you can optionally "tag" each string:

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'one: There is one apple|some: There are %count% apples'

'none_or_one: Il y a %count% pomme|some: Il y a %count% pommes'

The tags are really only hints for translators and don't affect the logic used to determine which plural form to use. The tags can be any descriptive string that ends with a colon (:). The tags also do not need to be the same in the original message as in the translated one.

Tip

As tags are optional, the translator doesn't use them (the translator will only get a string based on its position in the string).

Explicit Interval Pluralization

The easiest way to pluralize a message is to let the Translator use internal logic to choose which string to use based on a given number. Sometimes, you'll need more control or want a different translation for specific cases (for 0, or when the count is negative, for example). For such cases, you can use explicit math intervals:

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'{0} There are no apples|{1} There is one apple|]1,19] There are %count% apples|[20,Inf[ There are many apples'

The intervals follow the ISO 31-11 notation. The above string specifies four different intervals: exactly 0, exactly 1, 2-19, and 20 and higher.

You can also mix explicit math rules and standard rules. In this case, if the count is not matched by a specific interval, the standard rules take effect after removing the explicit rules:

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'{0} There are no apples|[20,Inf[ There are many apples|There is one apple|a_few: There are %count% apples'

For example, for 1 apple, the standard rule There is one apple will be used. For 2-19 apples, the second standard rule There are %count% apples will be selected.

An Interval can represent a finite set of numbers:

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{1,2,3,4}

Or numbers between two other numbers:

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[1, +Inf[
]-1,2[

The left delimiter can be [ (inclusive) or ] (exclusive). The right delimiter can be [ (exclusive) or ] (inclusive). Beside numbers, you can use -Inf and +Inf for the infinite.

Translations in Templates

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

Twig Templates

Symfony provides specialized Twig tags (trans and transchoice) to help with message translation of static blocks of text:

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{% trans %}Hello %name%{% endtrans %}

{% transchoice count %}
    {0} There are no apples|{1} There is one apple|]1,Inf[ There are %count% apples
{% endtranschoice %}

The transchoice tag automatically gets the %count% variable from the current context and passes it to the translator. This mechanism only works when you use a placeholder following the %var% pattern.

Caution

The %var% notation of placeholders is required when translating in Twig templates using the tag.

Tip

If you need to use the percent character (%) in a string, escape it by doubling it: {% trans %}Percent: %percent%%%{% endtrans %}

You can also pass some additional variables and specify the message domain:

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{% trans with {'%name%': 'Fabien'} into 'fr' %}Hello %name%{% endtrans %}

{% transchoice count with {'%name%': 'Fabien'} %}
    {0} %name%, there are no apples|{1} %name%, there is one apple|]1,Inf[ %name%, there are %count% apples
{% endtranschoice %}

{% trans with {'%name%': 'Fabien'} from 'custom_domain' %}Hello %name%{% endtrans %}

The trans and transchoice filters can be used to translate variable texts and complex expressions:

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{{ message|trans }}

{{ message|transchoice(5) }}

{{ message|trans({'%name%': 'Fabien'}, 'app') }}

{{ message|transchoice(5, {'%name%': 'Fabien'}, 'app') }}

Tip

Using the translation tags or filters have the same effect, but with one subtle difference: automatic output escaping is only applied to translations using a filter. In other words, if you need to be sure that your translated message is not output escaped, you must apply the raw filter after the translation filter:

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{# text translated between tags is never escaped #}
{% trans %}
    <h3>foo</h3>
{% endtrans %}

{% set message = '<h3>foo</h3>' %}

{# strings and variables translated via a filter are escaped by default #}
{{ message|trans|raw }}
{{ '<h3>bar</h3>'|trans|raw }}

Tip

You can set the translation domain for an entire Twig template with a single tag:

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{% trans_default_domain 'app' %}

Note that this only influences the current template, not any "included" template (in order to avoid side effects).

PHP Templates

The translator service is accessible in PHP templates through the translator helper:

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<?= $view['translator']->trans('Symfony is great') ?>

<?= $view['translator']->transChoice(
    '{0} There are no apples|{1} There is one apple|]1,Inf[ There are %count% apples',
    10,
    ['%count%' => 10]
) ?>

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'
);

$translator->transChoice(
    '{0} There are no apples|{1} There is one apple|]1,Inf[ There are %count% apples',
    10,
    [],
    '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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# updates the French translation file with the missing strings found in app/Resources/ 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:

  • the translations/ directory (at the root of the project);
  • the app/Resources/translations directory;
  • the app/Resources/<bundle name>/translations directory;
  • 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 any of the top 2 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: Domains are a way to organize messages into groups. Unless parts of the application are explicitly separated from each other, it is recommended to only use the default messages domain (e.g. messages.en.yaml).
  • 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, yml, 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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# app/config/config.yml
framework:
    translator:
        paths:
            - '%kernel.project_dir%/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.

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 doesn'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).

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.

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 just a few basic steps:

  • Abstract messages in your application by wrapping each in either the trans() or transChoice() methods;
  • 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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