A User-Agent and Host must be specified. The Content-Length must be specified and must be correct. Content-Length must be present and correct. Expected RPC 'methodCall', but got some other base type. No such method exists.
Programmer can usually throw a fault by using the die function.
Other common pitfalls. Permission denied errors usually caused by execute bit not being set for web server user properly. It, too, works by doing procedure calls over HTTP as XML documents. Unfortunately, SOAP appears to be suffering from specification creep. SOAP was originally created as a collaboration between UserLand, DevelopMentor and Microsoft.