PHP SOAP客户端无法正常工作

Question

I never developed a SOAP client, and now I have to do it and am having difficulties. This are the input parameters I have to send to the method "Agregar":

<Clientes>
    <Cliente>
        <Rut>123456785</Rut>
        <Nombre>123456785</Nombre>
    </Cliente>
</Clientes>

this is the testing code for the client I have done yet:

<?php
class Socio {
    function Socio($rut, $nombre) 
    {
        $this->nombre = $nombre;
        $this->rut = $rut;
    }
}

$client = new SoapClient("theurl...");

$socio = new Socio(156371777, "Sebastian");

$params = array(
  "Cliente" => $socio,
);

$response = $client->__soapCall("Agregar", $params);

var_dump($response);

but it is not working... I get the following error:

Fatal error: Uncaught SoapFault exception: [soap:Server] The server can't process the request. ---> The value cannot be null. Parameter name: s in /var/www/friends/awto/intouch/ccinterface.php:22 Stack trace: #0 /var/www/friends/awto/intouch/ccinterface.php(22): SoapClient->__soapCall('Agregar', Array) #1 {main} thrown in /var/www/friends/awto/intouch/ccinterface.php on line 22