PHP SOAP Client formats

Hi all,

ok, I am a little bit new to the SOAP game, but I understand it, and am 
using it to talk to an outside API.

The problem that I have is that the server that I am talking to (that is 
not in my control), will accept the following SOAP call

<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
  <soap:Body>
    <AuthenticateTest xmlns="https://api.authorize.net/soap/v1/">
      <merchantAuthentication>
        <name>name</name>
        <transactionKey>string</transactionKey>
      </merchantAuthentication>
    </AuthenticateTest>
  </soap:Body>
</soap:Envelope>


But it refuses a call that I have made using the SOAPClient PHP classes 
that look like this :

<?xml version="1.0" encoding="UTF-8"?>
<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/" xmlns:ns1="https://api.authorize.net/soap/v1/">
  <SOAP-ENV:Body>
    <ns1:AuthenticateTest>
      <merchantAuthentication>
        <name>name</name>
        <transactionKey>string</transactionKey>
      </merchantAuthentication>
    </ns1:AuthenticateTest>
  </SOAP-ENV:Body>
</SOAP-ENV:Envelope>

It appears that the one that PHP creates is all in line with all of the 
latest standards, and I know that the server is a Microsoft IIS server.

Does anyone know any parameters that I can use with the PHP SOAP client 
that could help me contruct the request like the top one???

I don't want to have to build the text myself, and open a socket and 
send the text manually like I did to verify that the top one works, and 
the bottom one doesn't.

Thanks,

Tim.