fXmlRpc\Transport\HttpAdapterTransport::send PHP Method

    public function send($endpoint, $payload)
    {
        try {
            $request = $this->messageFactory->createRequest('POST', $endpoint, ['Content-Type' => 'text/xml; charset=UTF-8'], $payload);
            $response = $this->client->sendRequest($request);
            if ($response->getStatusCode() !== 200) {
                throw HttpException::httpError($response->getReasonPhrase(), $response->getStatusCode());
            }
            return (string) $response->getBody();
        } catch (PsrHttpException $e) {
            $response = $e->getResponse();
            throw HttpException::httpError($response->getReasonPhrase(), $response->getStatusCode());
        } catch (ClientException $e) {
            throw TransportException::transportError($e);
        }
    }