protected function cc_format($number, $options)
    {
        if (empty($number)) {
            return '';
        }

        switch ($options) {
            case 'two_digits':
                $number = sprintf("%02d", $number);
                return substr($number, -2);
                break;
            case 'four_digits':
                return sprintf("%04d", $number);
                break;
            default:
                return $number;
                break;
        }
    }