Soap - Web service call in E-Verify

I have to utilize e-verify web services. Can anyone tell how to make call for E0-verify service and get response. Help would be appreciated. Right now i am using below code : But it always return bad request. Please let me know where i am wrong.

$url = "http://ift.tt/1OSlLaz";
$soapUser = "xxxxxxx";  
$soapPassword = "xxxxxxx";
$soap_options = array(
                'soap_version' => SOAP_1_2,
                'encoding' => 'UTF-8',                
                'location'=>$url
            );

            $soap_client = new SoapClient($url."?wsdl",$soap_options);