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Validates that all the elements of the given collection are unique (none of them is present more than once). By default elements are compared strictly, so '7' and 7 are considered different elements (a string and an integer, respectively). If you want to apply any other comparison logic, use the normalizer option.

See also

If you want to apply different validation constraints to the elements of a collection or want to make sure that certain collection keys are present, use the Collection constraint.

See also

If you want to validate that the value of an entity property is unique among all entities of the same type (e.g. the registration email of all users) use the UniqueEntity constraint.

Applies to property or method
Class Unique
Validator UniqueValidator

Basic Usage

This constraint can be applied to any property of type array or \Traversable. In the following example, $contactEmails is an array of strings:

  • Attributes
  • YAML
  • XML
  • PHP
// src/Entity/Person.php
namespace App\Entity;

use Symfony\Component\Validator\Constraints as Assert;

class Person
    protected $contactEmails;



type: array | string

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


type: string default: This collection should contain only unique elements.

This is the message that will be shown if at least one element is repeated in the collection.

You can use the following parameters in this message:

Parameter Description
{{ value }} The current (invalid) value


type: a PHP callable default: null

This option defined the PHP callable applied to each element of the given collection before checking if the collection is valid.

For example, you can pass the 'trim' string to apply the trim PHP function to each element of the collection in order to ignore leading and trailing whitespace during validation.


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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