public static function checkPhoneNumber($phoneNumber) {
        $phoneNumber = self::cleanPhoneNumber($phoneNumber);

        if (!empty($phoneNumber) && strlen($phoneNumber) > self::$_inputFldMaxLength['PhoneNumber']) {
            $errorMessage = 'The value for phone number can be no more than ' . self::$_inputFldMaxLength['PhoneNumber'] . ' characters, Please try again after making corrections';
            throw new HpsInvalidRequestException(
            HpsExceptionCodes::INVALID_PHONE_NUMBER, $errorMessage
            );
        }
        return $phoneNumber;
    }