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.
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:
- Enable and configure Symfony's translation service;
- Abstract strings (i.e. "messages") by wrapping them in calls to the
Translator
("Translations"); - Create translation resources/files for each supported locale that translate each message in the application;
- 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, XLIFF being the recommended format:
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<!-- 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.
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:
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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").
For details on how to handle this situation, see Using the Translator in the components documentation. For how to do this in templates, see Translations.
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.
To handle this, use the transChoice()
method or the transchoice
tag/filter in your template.
For much more information, see Using the Translator 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:
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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 specify the message domain and pass some additional variables:
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{% 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:
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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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<?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)
) ?>
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
$ ./app/console translation:update --dump-messages --force fr
# updates the English translation file with the missing strings found in AppBundle
$ ./app/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
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 defaultmessages
) - 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
,yml
, etc).
The loader can be the name of any registered loader. By default, Symfony provides many loaders, including:
xlf
: 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 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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# app/config/config.yml
framework:
translator:
paths:
- '%kernel.root_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.
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 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:
- First, Symfony looks for the translation in a
fr_FR
translation resource (e.g.messages.fr_FR.xlf
); - If it wasn't found, Symfony looks for the translation in a
fr
translation resource (e.g.messages.fr.xlf
); - If the translation still isn't found, Symfony uses the
fallbacks
configuration parameter, which defaults toen
(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 (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.