If you ever get the above error message in PHP, this probably means that instead of a wsdl file that you wanted to load, you got an error message from the webserver (that was nicely wrapped into HTML with a DTD). The case that took me 2 hours to investigate today was a "403 Forbidden" message instead of the actual wsdl file i had requested. 404 and 500 would also trigger this. The correct message would have been "unable to load WSDL". Maybe this is trivial, but if you hit this, it might help saving time.
