public function getMessage()
    {
        $message = null;

        if (isset($this->data->transactionResponse->messages)) {
            // In case of a successful transaction, a "messages" element is present
            $message = (string)$this->data->transactionResponse->messages->message->description;
        } elseif (isset($this->data->transactionResponse->errors)) {
            // In case of an unsuccessful transaction, an "errors" element is present
            $message = (string)$this->data->transactionResponse->errors->error->errorText;
        } elseif (isset($this->data->messages->message)) {
            // In case of invalid request, the top-level message provides details.
            $message = (string)$this->data->messages->message->text;
        }

        return $message;
    }