It was a great talk - thanks for coming up to present to us.
You mentioned how hard it can be to debug SOAP calls, especially when using different platforms at each end. One tool I have found immensely useful is soapUI, which can be used for free (there is a professional version too) and is obtained here: http://www.soapui.org/
I find that getting the SOAP interface working in that tool first will often highlight any potential problems with the API, and it is then much easier to move the service to a PHP consumer knowing how the service works, leaving just the implementation to be debugged.
I'm mentioning it because soapUI does not seem to be particularly well-known, but is a hidden gem.