PHP中的POST和XML的REST API在不应该返回时返回false？

So the makers of this API has my code clearly marked as functional, seeing as they made the damn thing. The thing is, that the REST API works fine as long as I use PI or QS alone. When I try to use the more advanced features requiring an XML document being sent with the REST request, it just returns false on the execution.

<?php

$objCurlToken = curl_init();
$strUrlToken = "https://servername/apimember/services/rest/connect/open/username/password/token";
$arrCurlOptions1 = array(
    CURLOPT_URL => $strUrlToken,
    CURLOPT_RETURNTRANSFER => true
);
curl_setopt_array($objCurlToken, $arrCurlOptions1);
$strXMLToken = curl_exec($objCurlToken);
$objXML = simplexml_load_string($strXMLToken);
curl_close($objCurlToken);


$strXMLPost = '
<?xml version="1.0" encoding="utf-8"?>
<synchroMember>
    <memberUID>
        EMAIL
    </memberUID>
    <dynContent>
        <entry>
            <key>
                EMAIL
            </key>
            <value>
                klaus@lagerbrau.de
            </value>
        </entry>
        <entry>
            <key>
                FIRSTNAME
            </key>
            <value>
                KLAUS LAGER
            </value>
        </entry>
        <entry>
            <key>
                EMVADMIN1
            </key>
            <value>
                This is klaus lager, the test subject
            </value>
        </entry>
    </dynContent>
</synchroMember>
';
$objCurlProbe = curl_init();
$strUrlProbe = "https://servername/apimember/services/rest/member/insertOrUpdateMember/" . $objXML->result . "";
$arrCurlOptions2 = array(
    CURLOPT_URL => $strUrlProbe,
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_POST => true,
    CURLOPT_POSTFIELDS => $strXMLPost
);
curl_setopt_array($objCurlProbe, $arrCurlOptions2);
$strCurlXMLResult = curl_exec($objCurlProbe);
echo "<pre>";
var_dump(htmlentities($objXML->result));
var_dump(htmlentities($strXMLPost));
var_dump(htmlentities($strCurlXMLResult));
curl_close($objCurlProbe);
$objXMLResult = simplexml_load_string($strCurlXMLResult);
var_dump($objXMLResult);
?>

The output looks as follows:

string(84) "*tokenkey*"
string(615) "
<?xml version="1.0" encoding="utf-8"?>
<synchroMember>
    <memberUID>
        EMAIL
    </memberUID>
    <dynContent>
        <entry>
            <key>
                EMAIL
            </key>
            <value>
                klaus@lagerbrau.de
            </value>
        </entry>
        <entry>
            <key>
                FIRSTNAME
            </key>
            <value>
                KLAUS LAGER
            </value>
        </entry>
        <entry>
            <key>
                EMVADMIN1
            </key>
            <value>
                This is klaus lager, the test subject
            </value>
        </entry>
    </dynContent>
</synchroMember>
"
string(0) ""
bool(false)

Taken from API documentation:

***Insert or Update Member Data***
This method searches a specified column of the Member table for a particular value used to identify a member
in order to update the member's data. If the member is not found, a new member is created. Any criteria can
be used to find the member including one of the fields to be updated.
The memberUID attribute is used to specify the key and value used as search criteria. The dynContent attribute
should only contain the values to be updated.
**insertOrUpdateMember**
***Input***
https://{server}/apimember/services/rest/member/insertOrUpdateMember/{token}
<?xml version="1.0" encoding="utf-8"?>
<synchroMember>
<memberUID>
{fieldNameA},
{fieldNameB}
</memberUID>
<dynContent>
<entry>
<key>>
{fieldNameA}
</key>
<value>
{fieldValueA}
</value>
</entry>
<entry>
<key>
{fieldNameB}
</key>
<value>
{fieldValueB}
</value>
</entry>
<entry>
<key>
{fieldNameC}
</key>
<value>
{fieldValueC}
</value>
</entry>
</dynContent>
</synchroMember>

I found the problem, the problem was in missing header describing the document as XML. As far as I know this shouldn't be a problem on normal REST servers, seeing as the only accepted data form is XML. What didn't help the matter is that the company is pretty horrible at software development, so the system never responds with errors and if it does, they are not human readable, and the company does not supply an error code list.