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:

// 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');

注解

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 chapter, 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 (“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.

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:

  • YAML
    # app/config/config.yml
framework:
    translator: { fallback: en }
  • XML
    <!-- app/config/config.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
        http://symfony.com/schema/dic/services/services-1.0.xsd
        http://symfony.com/schema/dic/symfony
        http://symfony.com/schema/dic/symfony/symfony-1.0.xsd">

    <framework:config>
        <framework:translator fallback="en" />
    </framework:config>
</container>
  • PHP
    // app/config/config.php
$container->loadFromExtension('framework', array(
    'translator' => array('fallback' => 'en'),
));

See Fallback Translation Locales for details on the fallback 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 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:

// ...
use Symfony\Component\HttpFoundation\Response;

public function indexAction()
{
    $translated = $this->get('translator')->trans('Symfony is great');

    return new Response($translated);
}

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:

  • XML
    <!-- messages.fr.xliff -->
<?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="1">
                <source>Symfony is great</source>
                <target>J'aime Symfony</target>
            </trans-unit>
        </body>
    </file>
</xliff>
  • YAML
    # messages.fr.yml
Symfony is great: J'aime Symfony
  • PHP
    // messages.fr.php
return array(
    '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.

The Translation Process

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

  • 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.
  • 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).

Message Placeholders

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

use Symfony\Component\HttpFoundation\Response;

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

    return new Response($translated);
}

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”).

For details on how to handle this situation, see Message Placeholders in the components documentation. For how to do this in templates, see Twig Templates.

Pluralization

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

There is one apple.
There are 5 apples.

To handle this, use the transChoice() method or the transchoice tag/filter in your template.

For much more information, see Pluralization in the Translation component documentation.

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:

{% 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.

警告

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

小技巧

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

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

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

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

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

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

{{ message|trans }}

{{ message|transchoice(5) }}

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

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

小技巧

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:

{# 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 }}

小技巧

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

{% trans_default_domain "app" %}

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

2.1 新版功能: The trans_default_domain tag was introduced in Symfony 2.1.

PHP Templates

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

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

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

Translation Resource/File Names and Locations

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

  • 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: An optional way to organize messages into groups (e.g. admin, navigation or the default messages) - see Using Message Domains;
  • 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. xliff, php, yml, etc).

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

  • xliff: XLIFF file;
  • php: PHP file;
  • yml: 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 xliff for translations. For more options, see Loading Message Catalogs.

注解

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.

警告

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:

$ php app/console cache:clear

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.xliff);
  2. If it wasn’t found, Symfony looks for the translation in a fr translation resource (e.g. messages.fr.xliff);
  3. If the translation still isn’t found, Symfony uses the fallback configuration parameter, which defaults to en (see Configuration).

Handling the User’s Locale

The locale of the current user is stored in the request and is accessible via the request object:

use Symfony\Component\HttpFoundation\Request;

public function indexAction(Request $request)
{
    $locale = $request->getLocale();

    $request->setLocale('en_US');
}

小技巧

Read Making the Locale “Sticky” during a User’s Session to learn how to store the user’s locale in the session.

See the The Locale and the URL section below about setting the locale via routing.

The Locale and the URL

Since you can store the locale of the user in the session, it may be tempting to use the same URL to display a resource in different languages based on the user’s locale. For example, http://www.example.com/contact could show content in English for one user and French for another user. Unfortunately, this violates a fundamental rule of the Web: that a particular URL returns the same resource regardless of the user. To further muddy the problem, which version of the content would be indexed by search engines?

A better policy is to include the locale in the URL. This is fully-supported by the routing system using the special _locale parameter:

  • YAML
    # app/config/routing.yml
contact:
    path:     /{_locale}/contact
    defaults: { _controller: AppBundle:Contact:index }
    requirements:
        _locale: en|fr|de
  • XML
    <!-- app/config/routing.xml -->
<?xml version="1.0" encoding="UTF-8" ?>
<routes xmlns="http://symfony.com/schema/routing"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://symfony.com/schema/routing
        http://symfony.com/schema/routing/routing-1.0.xsd">

    <route id="contact" path="/{_locale}/contact">
        <default key="_controller">AppBundle:Contact:index</default>
        <requirement key="_locale">en|fr|de</requirement>
    </route>
</routes>
  • PHP
    // app/config/routing.php
use Symfony\Component\Routing\RouteCollection;
use Symfony\Component\Routing\Route;

$collection = new RouteCollection();
$collection->add('contact', new Route(
    '/{_locale}/contact',
    array(
        '_controller' => 'AppBundle:Contact:index',
    ),
    array(
        '_locale'     => 'en|fr|de',
    )
));

return $collection;

When using the special _locale parameter in a route, the matched locale will automatically be set on the Request and can be retrieved via the getLocale() method. In other words, if a user visits the URI /fr/contact, the locale fr will automatically be set as the locale for the current request.

You can now use the locale to create routes to other translated pages in your application.

小技巧

Read How to Use Service Container Parameters in your Routes to learn how to avoid hardcoding the _locale requirement in all your routes.

Setting a default Locale

What if the user’s locale hasn’t been determined? You can guarantee that a locale is set on each user’s request by defining a default_locale for the framework:

  • YAML
    # app/config/config.yml
framework:
    default_locale: en
  • XML
    <!-- app/config/config.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
        http://symfony.com/schema/dic/services/services-1.0.xsd
        http://symfony.com/schema/dic/symfony
        http://symfony.com/schema/dic/symfony/symfony-1.0.xsd">

    <framework:config default-locale="en" />
</container>
  • PHP
    // app/config/config.php
$container->loadFromExtension('framework', array(
    'default_locale' => 'en',
));

2.1 新版功能: The default_locale parameter was defined under the session key originally, however, as of 2.1 this has been moved. This is because the locale is now set on the request instead of the session.

Translating Constraint Messages

If you’re using validation constraints with the form framework, then translating the error messages is easy: simply create a translation resource for the validators domain.

To start, suppose you’ve created a plain-old-PHP object that you need to use somewhere in your application:

// src/AppBundle/Entity/Author.php
namespace AppBundle\Entity;

class Author
{
    public $name;
}

Add constraints though any of the supported methods. Set the message option to the translation source text. For example, to guarantee that the $name property is not empty, add the following:

  • Annotations
    // src/AppBundle/Entity/Author.php
use Symfony\Component\Validator\Constraints as Assert;

class Author
{
    /**
     * @Assert\NotBlank(message = "author.name.not_blank")
     */
    public $name;
}
  • YAML
    # src/AppBundle/Resources/config/validation.yml
AppBundle\Entity\Author:
    properties:
        name:
            - NotBlank: { message: "author.name.not_blank" }
  • XML
    <!-- src/AppBundle/Resources/config/validation.xml -->
<?xml version="1.0" encoding="UTF-8" ?>
<constraint-mapping xmlns="http://symfony.com/schema/dic/constraint-mapping"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://symfony.com/schema/dic/constraint-mapping
        http://symfony.com/schema/dic/constraint-mapping/constraint-mapping-1.0.xsd">

    <class name="AppBundle\Entity\Author">
        <property name="name">
            <constraint name="NotBlank">
                <option name="message">author.name.not_blank</option>
            </constraint>
        </property>
    </class>
</constraint-mapping>
  • PHP
    // src/AppBundle/Entity/Author.php

// ...
use Symfony\Component\Validator\Mapping\ClassMetadata;
use Symfony\Component\Validator\Constraints\NotBlank;

class Author
{
    public $name;

    public static function loadValidatorMetadata(ClassMetadata $metadata)
    {
        $metadata->addPropertyConstraint('name', new NotBlank(array(
            'message' => 'author.name.not_blank',
        )));
    }
}

Create a translation file under the validators catalog for the constraint messages, typically in the Resources/translations/ directory of the bundle.

  • XML
    <!-- validators.en.xliff -->
<?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="1">
                <source>author.name.not_blank</source>
                <target>Please enter an author name.</target>
            </trans-unit>
        </body>
    </file>
</xliff>
  • YAML
    # validators.en.yml
author.name.not_blank: Please enter an author name.
  • PHP
    // validators.en.php
return array(
    'author.name.not_blank' => 'Please enter an author name.',
);

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.

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 (learn about this in Using the Translator);
  • 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.