Constraint_type::validate PHP Method

    public function validate($value)
    {
        if (!$value) {
            return true;
        }
        switch ($this->type) {
            case 'url':
                return filter_var($value, FILTER_VALIDATE_URL);
            case 'email':
                return filter_var($value, FILTER_VALIDATE_EMAIL);
            case 'number':
                return is_numeric($value);
            case 'integer':
                return is_int($value);
            case 'digits':
                return preg_match('/^[0-9]*$/', $value);
            case 'alphanum':
                return ctype_alnum($value);
        }
    }