I am using nusoap version 0.7.3. I have a simple client and server that use the default wsdl. I am trying to run a system('ls', $retval); command from the web service server and I keep getting the following error in the response from server to client:

Error: Response not of type text/xml: text/html


The apache log on the server side is getting this message.


[Wed Nov 12 16:33:34 2008] [error] [client 10.241.207.181] PHP Warning: Cannot modify header information - headers already sent in /usr/local/apache/htdocs/ws-server/nusoap.php on line 4179

Any help would be greatly appreciated