In a new article from PHPBuilder.com.au today, they talk about the "powerhouse of web services", SOAP, and how to get started working with it in PHP.

You've tried your hand at building mashups, experimented with a few RESTful Web services, maybe even started your own. Sure, you've got data sharing working. But how do you make your Web applications really talk to each other? In this tutorial, I'll show you how to take your Web applications to the next level with SOAP.

They opt to go with the NuSOAP method to consume another service and create your own simple one. They include a few code examples for either side and a (very) brief look at doing some debugging with what NuSOAP has to offer. One thing to note - if you have PHP5's SOAP extension compiled in and working, NuSOAP will throw an error about redeclaring a class name. This is because of a conflict between the naming of the SOAP extension's methods and NuSOAP.