Help needed with SOAP and PHP 5

Hi Experts, I have started learning PHP (version 5 )and SOAP. I am able to connect to the setup a connection and got the output of __getFunctions() method. When I am trying to call a function defined there which needs authentication and request in the following format,I am getting errors. <soapenv:Body> <savePurchaseOrder xmlns=”http://www.smartturn.com/services/OccamService/purchase-order”> <inCredential> <ns1:UserId xmlns:ns1=”http://www.smartturn.com/services/occamtypes”>testuser</ns1:Us erId> <ns2:Password xmlns:ns2=”http://www.smartturn.com/services/occamtypes”>testpassword</ns2:Password> I dont know how to pass the value of namespace (http://www.smartturn.com/services/OccamService/purchase-order) and credential information through __soapCall() function. Please let me know how to do this. Thanks in advance . -- Regards Nirmal