SOAP-ERROR: Parsing Schema: unexpected <element> in complexType

When trying to connect to a web service using the following

$client = new SoapClient("http://vocab.ndg.nerc.ac.uk/1.1/VocabServerAPI_dl.wsdl");

I get this error message

Fatal error: Uncaught SoapFault exception: [WSDL] SOAP-ERROR: Parsing Schema: unexpected in c开发者_如何学GoomplexTyp

Which seems odd as all I am doing is trying to connect to it not use any functions from it.

Does anyone know what would be causing this error?

The WSDL itself. There is something wrong with the way the WSDL is written when this error comes up. What exactly? I don't know.