In this new post on his weblog, Adam Trachtenberg goes into some detail as to "How ext/soap converts SOAP data structures to PHP".

I haven’t seen any documentation on how ext/soap converts SOAP results to PHP data structures, so I thought I would make a quick blog entry. If I get time, I will try to make this all pretty, confirm I am actually correct, and add it to the official docs.

Basically, the conversion is pretty simple: "Adam" becomes a "Person" attribute under a standard class. His attributed are also converted to sub-attributes, and, if there's both text and attributes already existing, it adds them to a "_" named property. That's pretty simplified - but a lot of the time, that's what can make things the best...