SOAP-ERROR: Parsing WSDL

Hello,

I am trying to connect to a webservice with WSDL but get the following 
error-message:

SOAP-ERROR: Parsing WSDL: Unknown required WSDL extension 
'http://schemas.xmlsoap.org/wsdl/soap/'

This is how I try to instanciate the Client:

$client=new 
SoapClient('http://api.rkd.reuters.com/schemas/wsdl/Charts_1_HttpAndRKDToken.wsdl');

I am new to webservices and therefore have no idea what is the problem 
and what might be a solution to this. Could anyone help me?

Thank you!
Harald