Introduction to Zend\Validator

The Zend\Validator component provides a set of commonly needed validators. It also provides a simple validator chaining mechanism by which multiple validators may be applied to a single datum in a user-defined order.

What is a validator?

A validator examines its input with respect to some requirements and produces a boolean result - whether the input successfully validates against the requirements. If the input does not meet the requirements, a validator may additionally provide information about which requirement(s) the input does not meet.

For example, a web application might require that a username be between six and twelve characters in length and may only contain alphanumeric characters. A validator can be used for ensuring that a username meets these requirements. If a chosen username does not meet one or both of the requirements, it would be useful to know which of the requirements the username fails to meet.

Basic usage of validators

Having defined validation in this way provides the foundation for Zend\Validator\ValidatorInterface, which defines two methods, isValid() and getMessages(). The isValid() method performs validation upon the provided value, returning TRUE if and only if the value passes against the validation criteria.

If isValid() returns FALSE, the getMessages() returns an array of messages explaining the reason(s) for validation failure. The array keys are short strings that identify the reasons for validation failure, and the array values are the corresponding human-readable string messages. The keys and values are class-dependent; each validation class defines its own set of validation failure messages and the unique keys that identify them. Each class also has a const definition that matches each identifier for a validation failure cause.

Note

The getMessages() methods return validation failure information only for the most recent isValid() call. Each call to isValid() clears any messages and errors caused by a previous isValid() call, because it’s likely that each call to isValid() is made for a different input value.

The following example illustrates validation of an e-mail address:

$validator = new Zend\Validator\EmailAddress();

if ($validator->isValid($email)) {
    // email appears to be valid
} else {
    // email is invalid; print the reasons
    foreach ($validator->getMessages() as $messageId => $message) {
        echo "Validation failure '$messageId': $message\n";
    }
}

Customizing messages

Validator classes provide a setMessage() method with which you can specify the format of a message returned by getMessages() in case of validation failure. The first argument of this method is a string containing the error message. You can include tokens in this string which will be substituted with data relevant to the validator. The token %value% is supported by all validators; this is substituted with the value you passed to isValid(). Other tokens may be supported on a case-by-case basis in each validation class. For example, %max% is a token supported by Zend\Validator\LessThan. The getMessageVariables() method returns an array of variable tokens supported by the validator.

The second optional argument is a string that identifies the validation failure message template to be set, which is useful when a validation class defines more than one cause for failure. If you omit the second argument, setMessage() assumes the message you specify should be used for the first message template declared in the validation class. Many validation classes only have one error message template defined, so there is no need to specify which message template you are changing.

$validator = new Zend\Validator\StringLength(8);

$validator->setMessage(
    'The string \'%value%\' is too short; it must be at least %min% ' .
    'characters',
    Zend\Validator\StringLength::TOO_SHORT);

if (!$validator->isValid('word')) {
    $messages = $validator->getMessages();
    echo current($messages);

    // "The string 'word' is too short; it must be at least 8 characters"
}

You can set multiple messages using the setMessages() method. Its argument is an array containing key/message pairs.

$validator = new Zend\Validator\StringLength(array('min' => 8, 'max' => 12));

$validator->setMessages( array(
    Zend\Validator\StringLength::TOO_SHORT =>
        'The string \'%value%\' is too short',
    Zend\Validator\StringLength::TOO_LONG  =>
        'The string \'%value%\' is too long'
));

If your application requires even greater flexibility with which it reports validation failures, you can access properties by the same name as the message tokens supported by a given validation class. The value property is always available in a validator; it is the value you specified as the argument of isValid(). Other properties may be supported on a case-by-case basis in each validation class.

$validator = new Zend\Validator\StringLength(array('min' => 8, 'max' => 12));

if (!$validator->isValid('word')) {
    echo 'Word failed: '
        . $validator->value
        . '; its length is not between '
        . $validator->min
        . ' and '
        . $validator->max
        . "\n";
}

Translating messages

Note

In versions 2.0 - 2.1, Zend\Validator\AbstractValidator implemented Zend\I18n\Translator\TranslatorAwareInterface and accepted instances of Zend\I18n\Translator\Translator. Starting in version 2.2.0, Zend\Validator now defines a translator interface, Zend\Validator\Translator\TranslatorInterface, as well as it’s own -aware variant, Zend\Validator\Translator\TranslatorAwareInterface. This was done to reduce dependencies for the component, and follows the principal of Separated Interfaces.

The upshot is that if you are migrating from a pre-2.2 version, and receiving errors indicating that the translator provided does not implement Zend\Validator\Translator\TranslatorInterface, you will need to make a change to your code.

An implementation of Zend\Validator\Translator\TranslatorInterface is provided in Zend\Mvc\I18n\Translator, which also extends Zend\I18n\Translator\Translator. This version can be instantiated and used just as the original Zend\I18n version.

A new service has also been registered with the MVC, MvcTranslator, which will return this specialized, bridge instance.

Most users should see no issues, as Zend\Validator\ValidatorPluginManager has been modified to use the MvcTranslator service internally, which is how most developers were getting the translator instance into validators in the first place. You will only need to change code if you were manually injecting the instance previously.

Validator classes provide a setTranslator() method with which you can specify an instance of Zend\Validator\Translator\TranslatorInterface which will translate the messages in case of a validation failure. The getTranslator() method returns the translator instance. Zend\Mvc\I18n\Translator provides an implementation compatible with the validator component.

$validator = new Zend\Validator\StringLength(array('min' => 8, 'max' => 12));
$translate = new Zend\Mvc\Translator\Translator();
// configure the translator...

$validator->setTranslator($translate);

With the static setDefaultTranslator() method you can set a instance of Zend\Validator\Translator\TranslatorInterface which will be used for all validation classes, and can be retrieved with getDefaultTranslator(). This prevents you from setting a translator manually for all validator classes, and simplifies your code.

$translate = new Zend\Mvc\I18n\Translator();
// configure the translator...

Zend\Validator\AbstractValidator::setDefaultTranslator($translate);

Sometimes it is necessary to disable the translator within a validator. To achieve this you can use the setDisableTranslator() method, which accepts a boolean parameter, and isTranslatorDisabled() to get the set value.

$validator = new Zend\Validator\StringLength(array('min' => 8, 'max' => 12));
if (!$validator->isTranslatorDisabled()) {
    $validator->setDisableTranslator();
}

It is also possible to use a translator instead of setting own messages with setMessage(). But doing so, you should keep in mind, that the translator works also on messages you set your own.