$client = new SoapClient("some.wsdl");
and $client is now an object which has class methods as defined in some.wsdl. So if there was a method called getTime in the WSDL then you would just call:
$result = $client->getTime();
And the result of that would (obviously) be in the $result variable. You can use the __getFunctions method to return a list of all the available methods.