Wrong request generation soap client php

I'm trying to make a request to a soap webservice of mine.

    class DateTime2 extends DateTime {
        function __toString() { 
            return $this->format("d/m/Y H:i");
        }
    }
    $date = new DateTime2();

    $client = new SoapClient("http://www.myos.it/sp/smartphonelayer.asmx?wsdl",array("trace" => 1));
    $result = $client->SetReservation("Mario Rossi",2,"01234567",$date."");
    echo "REQUEST:".$client->__getLastRequest()."<br>"; 
    print_r($result);

The output i get is:

<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/" xmlns:ns1="http://tempuri.org/">
    <SOAP-ENV:Body>
        <ns1:SetReservation/>
        <param1>2</param1>
        <param2>12345678</param2>
        <param3>2011-08-30T07:10:32</param3>
    </SOAP-ENV:Body>
</SOAP-ENV:Envelope>
<br>stdClass Object
(
  [SetReservationResult] => stdClass Object
     (
         [Success] => SqlDateTime overflow. Must be between 1/1/1753 12:00:00 AM and 12/31/9999 11:59:59 PM.
            [DeskCode] => 
            [Message] => 
       )

)

As you can see i get only 3 parameters in request created by soapClient when i give it 4 parameteres.

For Sending the Parameter you need to use the array()

Also for Date Time, XML needs following format

class DateTime2 extends DateTime {
    function __toString() { 
        return $this->format("Y-m-d\TH:i:s.000\Z");
    }
}
$date = new DateTime2();
$client = new SoapClient("http://www.myos.it/sp/smartphonelayer.asmx?wsdl",array("trace" => 1));

$result = $client->SetReservation(array( "RDescription"=>"Giuseppe Silvestri",
                                         "RNumber"=>2,
                                         "RPhoneNumber"=>"3286026817",
                                         "RDate"=>$date.""));
echo "REQUEST:".$client->__getLastRequest()."<br>"; 
print_r($result);