Php wsdl soapclient request

I have a web server and wsdl I have to create a webclient php to login

svc:
http://5.249.140.31:9100/wsAccesso.svc
wsdl:
http://5.249.140.31:9100/wsAccesso.svc?singleWsdl

I've tried to create PHP code but I always get SoapFault

$requestParams = array(
        'impianto' => 'string',
        'userName' => 'string',
        'password' => 'string',
        'userType' => 'number'
);

$client = new SoapClient('http://5.249.140.31:9100/wsAccesso.svc?singleWsdl',array('trace'=> 2, 'exceptions' => 0, 'cache_wsdl' => WSDL_CACHE_NONE, 'features' => SOAP_SINGLE_ELEMENT_ARRAYS));

$response = $client->Login($requestParams);

var_dump($response);

I am almost sure that the problem is in the management of the calls Login

you can use directly xml in the call ?