Validators

Callback Validator

Laminas\Validator\Callback allows you to provide a callback with which to validate a given value.

Supported options

The following options are supported for Laminas\Validator\Callback:

• callback: Sets the callback which will be called for the validation.
• callbackOptions: Sets the additional options which will be given to the validator and/or callback.
• throwExceptions: When true, allows exceptions thrown inside of callbacks to propagate.
• bind: When true, the callback will be bound to the scope of the validator instance

Basic usage

The simplest use case is to pass a function as a callback. Consider the following function:

function myMethod($value)
{
    // some validation
    return true;
}

To use it within Laminas\Validator\Callback, pass it to the constructor

$valid = new Laminas\Validator\Callback('myMethod');
if ($valid->isValid($input)) {
    // input appears to be valid
} else {
    // input is invalid
}

Usage with closures

The Callback validator supports any PHP callable, including PHP closures.

$valid = new Laminas\Validator\Callback(function($value) {
    // some validation
    return true;
});

if ($valid->isValid($input)) {
    // input appears to be valid
} else {
    // input is invalid
}

Usage with class-based callbacks

Of course it's also possible to use a class method as callback. Consider the following class definition:

class MyClass
{
    public function myMethod($value)
    {
        // some validation
        return true;
    }
}

To use it with the Callback validator, pass a callable using an instance of the class:

$valid = new Laminas\Validator\Callback([new MyClass, 'myMethod']);
if ($valid->isValid($input)) {
    // input appears to be valid
} else {
    // input is invalid
}

You may also define a static method as a callback. Consider the following class definition and validator usage:

class MyClass
{
    public static function test($value)
    {
        // some validation
        return true;
    }
}

$valid = new Laminas\Validator\Callback([MyClass::class, 'test']);
if ($valid->isValid($input)) {
    // input appears to be valid
} else {
    // input is invalid
}

Finally, you may define the magic method __invoke() in your class. If you do so, you can provide a class instance itself as the callback:

class MyClass
{
    public function __invoke($value)
    {
        // some validation
        return true;
    }
}

$valid = new Laminas\Validator\Callback(new MyClass());
if ($valid->isValid($input)) {
    // input appears to be valid
} else {
    // input is invalid
}

Adding options

Laminas\Validator\Callback also allows the usage of options which are provided as additional arguments to the callback.

Consider the following class and method definition:

class MyClass
{
    public static function myMethod($value, $option)
    {
        // some validation
        return true;
    }

    /**
     * Or, to use with contextual validation
     */
    public static function myMethod($value, $context, $option)
    {
        // some validation
        return true;
    }

}

There are two ways to inform the validator of additional options: pass them in the constructor, or pass them to the setOptions() method.

To pass them to the constructor, you would need to pass an array containing two keys, callback and callbackOptions:

$valid = new Laminas\Validator\Callback([
    'callback'        => [MyClass::class, 'myMethod'],
    'callbackOptions' => $options,
]);

if ($valid->isValid($input)) {
    // input appears to be valid
} else {
    // input is invalid
}

Otherwise, you may pass them to the validator after instantiation:

$valid = new Laminas\Validator\Callback([MyClass::class, 'myMethod']);
$valid->setOptions($options);

if ($valid->isValid($input)) {
    // input appears to be valid
} else {
    // input is invalid
}

When there are additional values given to isValid(), then these values will be passed as an additional argument:

$valid = new Laminas\Validator\Callback([MyClass::class, 'myMethod']);
$valid->setOptions($options);

if ($valid->isValid($input, $context)) {
    // input appears to be valid
} else {
    // input is invalid
}

When making the call to the callback, the value to be validated will always be passed as the first argument to the callback followed by all other values given to isValid(); all other options will follow it. The amount and type of options which can be used is not limited.

Callbacks and Scope

By default, callbacks are executed in their own scope and do not have access to the validator instance they are executed in.

It is possible to bind your callback to the validator scope by setting the bind option to true.

This is useful when you wish to provide more detailed error messages in case there are multiple potential reasons for validation failure:

$validator = new Laminas\Validator\Callback([
    'callback' => function (mixed $value): bool {
        if ($value === 42) {
            $this->setMessage(
                'Sorry, the meaning of life is not acceptable',
                 Laminas\Validator\Callback::INVALID_VALUE,
            );

            return false;
        }

        if ($value === 'goats') {
            $this->setMessage(
                'Sorry, I don’t like goats…',
                 Laminas\Validator\Callback::INVALID_VALUE,
            );

            return false;
        }

        return true;
    },
    'bind' => true,
]);

Binding only occurs when the callback option and the bind option are used in the constructor via an options array as shown above.

Exceptions within Callbacks

By default, the callback validator will catch any Exception thrown inside the callback and return false. The error message will indicate callback failure as opposed to invalid input.

There is a third option throwExceptions that when true will re-throw exceptions that occur inside the callback.

This is primarily useful in a development environment when you are testing callbacks and need to catch and verify exceptions thrown by your own application.

For example:

$callback = static function (mixed $value): bool {
    if ($value === true) {
        return true;
    }

    throw new ApplicationException('Bad news');
}

$validator = new Laminas\Validator\Callback([
    'callback' => $callback,
    'throwExceptions' => true,
]);

$validator->isValid('Nope'); // An exception is thrown