Adam Trachtenburg has linked two resources that PHP5 developers out there working with SOAP might find handy:

• Writing SOAP clients and servers with PHP5 - a presentation from Michael Rasmussen
• Webservice Helper - WSDL generator PHP 5 - just what it says, a library to help with the creation of web services with SOAP, including creating the WSDL file.

Neither of these were tested by Adam but they both definitely sound interesting (and both pretty up-to-date).