Callback Validator

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

Supported options

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

• callback: Sets the callback which will be called for the validation.
• options: Sets the additional options which will be given to the validator and/or callback.

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 Zend\Validator\Callback, pass it to the constructor

$valid = new Zend\Validator\Callback('myMethod');
if ($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.

$valid = new Zend\Validator\Callback(function($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:

$valid = new Zend\Validator\Callback([new MyClass, 'myMethod']);
if ($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;
    }
}

$valid = new Zend\Validator\Callback(MyClass::class, 'test']);
if ($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;
    }
}

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

Adding options

Zend\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 Zend\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 Zend\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 Zend\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.