Luhn

This constraint is used to ensure that a credit card number passes the Luhn algorithm. It is useful as a first step to validating a credit card: before communicating with a payment gateway.

Applies to	property or method
Class	Luhn
Validator	LuhnValidator

Basic Usage

To use the Luhn validator, apply it to a property on an object that will contain a credit card number.

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

use Symfony\Component\Validator\Constraints as Assert;

class Transaction
{
    #[Assert\Luhn(message: 'Please check your credit card number.')]
    protected string $cardNumber;
}
    

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        # config/validator/validation.yaml
App\Entity\Transaction:
    properties:
        cardNumber:
            - Luhn:
                message: Please check your credit card number.
    

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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\Transaction">
        <property name="cardNumber">
            <constraint name="Luhn">
                <option name="message">Please check your credit card number.</option>
            </constraint>
        </property>
    </class>
</constraint-mapping>
    

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

use Symfony\Component\Validator\Constraints as Assert;
use Symfony\Component\Validator\Mapping\ClassMetadata;

class Transaction
{
    // ...

    public static function loadValidatorMetadata(ClassMetadata $metadata): void
    {
        $metadata->addPropertyConstraint('cardNumber', new Assert\Luhn([
            'message' => 'Please check your credit card number',
        ]));
    }
}
    

Note

As with most of the other constraints, null and empty strings are considered valid values. This is to allow them to be optional values. If the value is mandatory, a common solution is to combine this constraint with NotBlank.

Options

`groups`

type: array | string default: null

It defines the validation group or groups of this constraint. Read more about validation groups.

`message`

type: string default: Invalid card number.

The default message supplied when the value does not pass the Luhn check.

You can use the following parameters in this message:

Parameter	Description
`{{ value }}`	The current (invalid) value
`{{ label }}`	Corresponding form field label

`payload`

type: mixed default: null

This option can be used to attach arbitrary domain-specific data to a constraint. The configured payload is not used by the Validator component, but its processing is completely up to you.

For example, you may want to use several error levels to present failed constraints differently in the front-end depending on the severity of the error.

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

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