The Validator Component

Installation

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$ composer require symfony/validator:^3.4

Usage

The Validator component behavior is based on two concepts:

• Constraints, which define the rules to be validated;
• Validators, which are the classes that contain the actual validation logic.

The following example shows how to validate that a string is at least 10 characters long:

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use Symfony\Component\Validator\Constraints\Length;
use Symfony\Component\Validator\Constraints\NotBlank;
use Symfony\Component\Validator\Validation;

$validator = Validation::createValidator();
$violations = $validator->validate('Bernhard', [
    new Length(['min' => 10]),
    new NotBlank(),
]);

if (0 !== count($violations)) {
    // there are errors, now you can show them
    foreach ($violations as $violation) {
        echo $violation->getMessage().'<br>';
    }
}

The validate() method returns the list of violations as an object that implements ConstraintViolationListInterface. If you have lots of validation errors, you can filter them by error code:

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use Symfony\Bridge\Doctrine\Validator\Constraints\UniqueEntity;

$violations = $validator->validate(...);
if (0 !== count($violations->findByCodes(UniqueEntity::NOT_UNIQUE_ERROR))) {
    // handle this specific error (display some message, send an email, etc.)
}

Retrieving a Validator Instance

The Validator object (that implements ValidatorInterface) is the main access point of the Validator component. To create a new instance of it, it's recommended to use the Validation class:

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use Symfony\Component\Validator\Validation;

$validator = Validation::createValidator();

This $validator object can validate simple variables such as strings, numbers and arrays, but it can't validate objects. To do so, configure the Validator as explained in the next sections.

Learn More