public function isValid(): bool
    {
        return $this->result_code === ResponseInterface::RESULT_OK
            || $this->result_code === ResponseInterface::RESULT_RECEIPT_VALID_BUT_SUB_EXPIRED;
    }
public function isValid(): bool
    {
        return $this->result_code === ResponseInterface::RESULT_OK
            || $this->result_code === ResponseInterface::RESULT_RECEIPT_VALID_BUT_SUB_EXPIRED;
    }
public function isValid ( ) : bool { return $ this -> result_code === ResponseInterface :: RESULT_OK || $ this -> result_code === ResponseInterface :: RESULT_RECEIPT_VALID_BUT_SUB_EXPIRED ; }
returns if the receipt is valid or not

@return boolean
returns if the receipt is valid or not