CakePHP Validate Masked Credit Card With Regex
===

I am creating an update billing information section for my users. I am currently passing a masked credit card number to the form. I do not want the user to have to update their credit card information if they only want to update say their billing address.

I am attempting to use regex to match the masked credit card, but I have not been able to get ANY regex patterns to match... Even 100% wildcards...

Here are couple of examples of what I have tried...

================================================================

The Masked Credit Card Value Is XXXXXXXXXXXX0012

================================================================

    'creditcard' => array(
             'creditcard' => array(
    			'rule' => array('cc', 'all', false, '^[.]+$'),
    			'message' => 'Required',
    			'allowEmpty' => false,
    			'required' => true,
    			),
    	),

================================================================

    	'creditcard' => array(
    		'creditcard' => array(
    			'rule' => array('cc', 'all', false, '/^[X]+[0-9](4,)$/'),
    			'message' => 'Required',
    			'allowEmpty' => false,
    			'required' => true,
    			),
    	),

================================================================

    	'creditcard' => array(
    		'creditcard' => array(
    			'rule' => array('cc', 'all', false, '/^[x]+[0-9]+$/i'),
    			'message' => 'Required',
    			'allowEmpty' => false,
    			'required' => true,
    			),
    	),
    

Any Ideas Are Greatly Appreciated!

Thank You!!