SOAP error for php

Question

Hi, I'm using http://www.php.net/manual/en/book.soap.php and I'm getting this error "Method Not Allowed"

$wsdl_url = "http://192.168.100.165:9080/service/service?wsdl";
$client = new SoapClient($wsdl_url); 
$userName = "hello";
$password = "testing";
$test = "OK";
$login = $client->ClientOperation(array("userName"=>$userName,
                                "password"=>$password,
                                "test"=>test)
                      );
var_dump($login);
}
catch (SoapFault $login) {
var_dump($login);
}

What could be the problem?