XML：Post返回空值

Question

以下代码用于发送和短信。但它返回null。有时我可以发送短信但仍然返回值为空。我在Web应用程序中使用此代码来发送短信。 代码中是否有语法错误，或者您可以帮我找到以下代码中的错误。

   $xmlstring = "<?xml version='1.0' encoding='UTF-8' ?>
    <TELEMESSAGE>
        <TELEMESSAGE_CONTENT>
            <MESSAGE>
                <MESSAGE_INFORMATION>
                    <SUBJECT></SUBJECT>
                </MESSAGE_INFORMATION>
                <USER_FROM>
                    <CIML>
                        <NAML>
                            <LOGIN_DETAILS>
                                <USER_NAME>username</USER_NAME>
                                <PASSWORD>password</PASSWORD>
                            </LOGIN_DETAILS>
                        </NAML>
                    </CIML>
                </USER_FROM>
                <MESSAGE_CONTENT>
                    <TEXT_MESSAGE>
                        <MESSAGE_INDEX>0</MESSAGE_INDEX>
                        <TEXT>TEST MESSAGE</TEXT>
                    </TEXT_MESSAGE>
                </MESSAGE_CONTENT>
                <USER_TO>
                    <CIML>
                        <DEVICE_INFORMATION>
                            <DEVICE_TYPE DEVICE_TYPE='SMS'/>
                            <DEVICE_VALUE>7707070</DEVICE_VALUE>
                        </DEVICE_INFORMATION>
                    </CIML>
                </USER_TO>
            </MESSAGE>
        </TELEMESSAGE_CONTENT>
        <VERSION>1.6</VERSION>
    </TELEMESSAGE>"; 

        //creating header for http post request
        $myHeader = array(
            "MIME-Version: 1.0",
            "Content-type: text/xml; charset=utf-8"
        );
        //creating and initiating curl
        $ch = curl_init();

        //setting curl/http headers
        curl_setopt($ch, CURLOPT_POST, 1);
        curl_setopt($ch, CURLOPT_POSTFIELDS, $xmlstring);
        curl_setopt($ch, CURLOPT_URL, "http://bulkmessage.com.mv/partners/xmlMessage.jsp");
        curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 2);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
        curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
        curl_setopt($ch, CURLOPT_HTTPHEADER, $myHeader);
        //executing http request and getting response. $postResult will contain response xml from TeleMessage.
        $postResult = curl_exec($ch);


       //dd($postResult);
        if (curl_errno($ch)) {
            return null;
            /*
            * for PHP5 you can throw Exception:
            * throw new Exception("Error while sending");
            */
        }
        curl_close($ch);

        $xmlPostResult = simplexml_load_string($postResult);
        $apimsgid = $xmlPostResult->TELEMESSAGE_CONTENT->RESPONSE->MESSAGE_ID;
        $apimsgkey = $xmlPostResult->TELEMESSAGE_CONTENT->RESPONSE->MESSAGE_KEY;
        $response = $xmlPostResult->TELEMESSAGE_CONTENT->RESPONSE->RESPONSE_STATUS;