Validator Chains

Often, multiple validations should be applied to some value in a particular order. The following code demonstrates a way to solve the example from the introduction, where a username must be between 6 and 12 alphanumeric characters:

use Zend\I18n\Validator\Alnum;
use Zend\Validator\StringLength;
use Zend\Validator\ValidatorChain;

// Create a validator chain and add validators to it
$chain = new ValidatorChain();
$chain->attach(new StringLength(['min' => 6, 'max' => 12]));
$chain->attach(new Alnum());

// Validate the username
if ($validatorChain->isValid($username)) {
    // username passed validation
} else {
    // username failed validation; print reasons
    foreach ($validatorChain->getMessages() as $message) {
        echo "$message\n";
    }
}

Validators are run in the order they were added to the ValidatorChain. In the above example, the username is first checked to ensure that its length is between 6 and 12 characters, and then it is checked to ensure that it contains only alphanumeric characters. The second validation, for alphanumeric characters, is performed regardless of whether the first validation, for length between 6 and 12 characters, succeeds. This means that if both validations fail, getMessages() will return failure messages from both validators.

In some cases, it makes sense to have a validator break the chain if its validation process fails. ValidatorChain supports such use cases with the second parameter to the attach() method. By setting $breakChainOnFailure to true, if the validator fails, it will short-circuit execution of the chain, preventing subsequent validators from executing. If the above example were written as follows, then the alphanumeric validation would not occur if the string length validation fails:

$chain->attach(new StringLength(['min' => 6, 'max' => 12], true));
$chain->attach(new Alnum());

Any object that implements Zend\Validator\ValidatorInterface may be used in a validator chain.

Setting Validator Chain Order

For each validator added to the ValidatorChain, you can set a priority to define the chain order. The default value is 1. Higher values indicate earlier execution, while lower values execute later; use negative values to force late execution.

In the following example, the username is first checked to ensure that its length is between 7 and 9 characters, and then it is checked to ensure that its length is between 3 and 5 characters.

use Zend\I18n\Validator\Alnum;
use Zend\Validator\StringLength;
use Zend\Validator\ValidatorChain;

$username = 'ABCDFE';

// Create a validator chain and add validators to it
$chain = new ValidatorChain();
$chain->attach(
    new StringLength(['min' => 3, 'max' => 5]),
    true, // break chain on failure
    1
);
$chain->attach(
    new StringLength(['min' => 7, 'max' => 9]),
    true, // break chain on failure
    2     // higher priority!
);

// Validate the username
if ($validatorChain->isValid($username)) {
    // username passed validation
    echo "Success";
} else {
    // username failed validation; print reasons
    foreach ($validatorChain->getMessages() as $message) {
        echo "$message\n";
    }
}

// This first example will display: The input is less than 7 characters long