Just a very short tip as it was a big surprise to me :) If you have xdebug enabled SoapClient will not throw an exception but cause a fatal error.

All you have to do is disable xdebug or make sure that soap service is available.

Since i am writing about PHP SoapClient it is worth to mention that wsdl is cached in tmp folder on the servers. Most of web service errors that i got were caused by wsdl being cached on the server even that service has changed.