# KeyOptional - `KeyOptional(string|int $key, Validator $validator)` Validates the value of an array against a given validator when the key exists. ```php v::keyOptional('name', v::stringType())->assert([]); // Validation passes successfully v::keyOptional('name', v::stringType())->assert(['name' => 'The Respect Panda']); // Validation passes successfully v::keyOptional('email', v::email())->assert([]); // Validation passes successfully v::keyOptional('email', v::email())->assert(['email' => 'therespectpanda@gmail.com']); // Validation passes successfully v::keyOptional('age', v::intVal())->assert(['age' => 'Twenty-Five']); // → `.age` must be an integer ``` The name of this validator is automatically set to the key name. ```php v::keyOptional('age', v::intVal())->assert(['age' => 'Twenty-Five']); // → `.age` must be an integer ``` ## Note This validator will pass for anything that is not an array because it will always pass when it doesn't find a key. If you want to ensure the input is an array, use [ArrayType](ArrayType.md) with it. ```php v::arrayType()->keyOptional('phone', v::phone())->assert('This is not an array'); // → "This is not an array" must be an array ``` Below are some other validators that are tightly related to `KeyOptional`: - To validate if a key exists, use [KeyExists](KeyExists.md) instead. - To validate an array against a given validator requiring the key to exist, use [Key](Key.md) instead. ## Templates ## Template placeholders | Placeholder | Description | | ----------- | ---------------------------------------------------------------- | | `subject` | The validated input or the custom validator name (if specified). | ## Categorization - Arrays - Structures ## Changelog | Version | Description | | ------: | :------------------------- | | 3.0.0 | Created from [Key](Key.md) | ## See Also - [ArrayType](ArrayType.md) - [ArrayVal](ArrayVal.md) - [Each](Each.md) - [Key](Key.md) - [KeyExists](KeyExists.md) - [Property](Property.md) - [PropertyExists](PropertyExists.md) - [PropertyOptional](PropertyOptional.md) [array]: https://www.php.net/array [ArrayAccess]: https://www.php.net/arrayaccess