How to Translate Validation Constraint Messages

The validation constraints used in forms can translate their error messages by creating a translation resource for the validators translation domain.

First of all, install the Symfony translation component (if it's not already installed in your application) running the following command:

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        $ composer require symfony/translation
    

Suppose you've created a plain-old-PHP object that you need to use somewhere in your application:

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

class Author
{
    public $name;
}
    

Add constraints through 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
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        // src/Entity/Author.php
namespace App\Entity;

use Symfony\Component\Validator\Constraints as Assert;

class Author
{
    /**
     * @Assert\NotBlank(message="author.name.not_blank")
     */
    public $name;
}
    

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        # config/validator/validation.yaml
App\Entity\Author:
    properties:
        name:
            - NotBlank: { message: 'author.name.not_blank' }
    

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        <!-- config/validator/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
        https://symfony.com/schema/dic/constraint-mapping/constraint-mapping-1.0.xsd">

    <class name="App\Entity\Author">
        <property name="name">
            <constraint name="NotBlank">
                <option name="message">author.name.not_blank</option>
            </constraint>
        </property>
    </class>
</constraint-mapping>
    

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

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

class Author
{
    public $name;

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

Now, create a validators catalog file in the translations/ directory:

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        <!-- translations/validators/validators.en.xlf -->
<?xml version="1.0" encoding="UTF-8" ?>
<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="author.name.not_blank">
                <source>author.name.not_blank</source>
                <target>Please enter an author name.</target>
            </trans-unit>
        </body>
    </file>
</xliff>
    

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        # translations/validators/validators.en.yaml
author.name.not_blank: Please enter an author name.
    

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        // translations/validators/validators.en.php
return [
    'author.name.not_blank' => 'Please enter an author name.',
];
    

You may need to clear your cache (even in the dev environment) after creating this file for the first time.

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