This definition technique allows for better control of how the validation rules work. But before we discuss that, let’s see the general usage pattern adding a rule for a single field:

var $validate = array(
    'fieldName1' => array(
        'rule' => 'ruleName', // or: array('ruleName', 'param1', 'param2' ...)
        'required' => true,
        'allowEmpty' => false,
        'on' => 'create', // or: 'update'
        'message' => 'Your Error Message'
    )
);

1. var $validate = array(
2. 'fieldName1' => array(
3. 'rule' => 'ruleName', // or: array('ruleName', 'param1', 'param2' ...)
4. 'required' => true,
5. 'allowEmpty' => false,
6. 'on' => 'create', // or: 'update'
7. 'message' => 'Your Error Message'
8. )
9. );

The 'rule' key is required. If you only set 'required' => true, the form validation will not function correctly. This is because 'required' is not actually a rule.

As you can see here, each field (only one field shown above) is associated with an array that contains five keys: ‘rule’, ‘required’, ‘allowEmpty’, ‘on’ and ‘message’. Let’s have a closer look at these keys.