Using the Translator

Using the Translator

Imagine you want to translate the string "Symfony is great" into French:

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use Symfony\Component\Translation\Translator;
use Symfony\Component\Translation\Loader\ArrayLoader;

$translator = new Translator('fr_FR');
$translator->addLoader('array', new ArrayLoader());
$translator->addResource('array', array(
    'Symfony is great!' => 'J\'aime Symfony!',
), 'fr_FR');

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

In this example, the message "Symfony is great!" will be translated into the locale set in the constructor (fr_FR) if the message exists in one of the message catalogs.

Message Placeholders

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

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

echo $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"). 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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// ...
$translated = $translator->trans(
    'Hello %name%',
    array('%name%' => $name)
);

echo $translated;

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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    <?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>Hello %name%</source>
                    <target>Bonjour %name%</target>
                </trans-unit>
            </body>
        </file>
    </xliff>
    
  • PHP
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    return array(
        'Hello %name%' => 'Bonjour %name%',
    );
    
  • YAML
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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.

Creating Translations

The act of creating translation files is an important part of "localization" (often abbreviated L10n). Translation files consist of a series of id-translation pairs for the given domain and locale. The source is the identifier for the individual translation, and can be the message in the main locale (e.g. "Symfony is great") of your application or a unique identifier (e.g. symfony.great - see the sidebar below).

Translation files can be created in several different formats, XLIFF being the recommended format. These files are parsed by one of the loader classes.

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    <?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>
                <trans-unit id="2">
                    <source>symfony.great</source>
                    <target>J'aime Symfony</target>
                </trans-unit>
            </body>
        </file>
    </xliff>
    
  • YAML
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    Symfony is great: J'aime Symfony
    symfony.great:    J'aime Symfony
    
  • PHP
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    return array(
        'Symfony is great' => 'J\'aime Symfony',
        'symfony.great'    => 'J\'aime Symfony',
    );
    

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.

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:
            great: Symfony is great
            amazing: Symfony is amazing
        has:
            bundles: Symfony has bundles
    user:
        login: Login
    
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    array(
        'symfony' => array(
            'is' => array(
                'great'   => 'Symfony is great',
                'amazing' => 'Symfony is amazing',
            ),
            'has' => array(
                'bundles' => 'Symfony has bundles',
            ),
        ),
        'user' => array(
            'login' => 'Login',
        ),
    );
    

The multiple levels are flattened into single id/translation pairs by adding a dot (.) between every level, therefore the above examples are equivalent to the following:

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    symfony.is.great: Symfony is great
    symfony.is.amazing: Symfony is amazing
    symfony.has.bundles: Symfony has bundles
    user.login: Login
    
  • PHP
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    return array(
        'symfony.is.great'    => 'Symfony is great',
        'symfony.is.amazing'  => 'Symfony is amazing',
        'symfony.has.bundles' => 'Symfony has bundles',
        'user.login'           => 'Login',
    );
    

Pluralization

Message pluralization is a tough topic as the rules can be quite complex. For instance, here is the mathematic representation of the Russian pluralization rules:

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(($number % 10 == 1) && ($number % 100 != 11))
    ? 0
    : ((($number % 10 >= 2)
        && ($number % 10 <= 4)
        && (($number % 100 < 10)
        || ($number % 100 >= 20)))
            ? 1
            : 2
);

As you can see, in Russian, you can have three different plural forms, each given an index of 0, 1 or 2. For each form, the plural is different, and so the translation is also different.

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 pluralized messages, use the transChoice() method:

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

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.

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.

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',
    array(),
    'messages',
    'fr_FR'
);

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

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