I know nothing about PHP so this may be completely wrong but does PHP interpret an underscore in function names as something special, like to define a member function?
Zippo mentions that there's a Rename object of some sort in PHP (which I think he's found by listing all objects) and the function name is Rename_GetNewName so I wonder if that's turning into a GetNewName function on an object called Rename rather than a Rename_GetNewName function with global scope?