The Zend Framework ships with SOAP functionality and one especially neat class called Zend_Soap_AutoDiscover.  This class uses a comment docblock to auto-generate a WSDL at runtime.  I won't go into the details how it works here, but you can check the Zend Framework documentation for an example.  When using this class at work, I noticed the WSDL would not always generate correctly.  After a lot of digging around, I found the cause: eAccelerator.