Empty var when sending data from Flash CS5 to Zend_AMF service

Question

After working with Flex and Zend_AMF i'm now working for another project (little game) with Flash CS5 and Zend_AMF. Retrieving data goes perfectly as long as i manage all the parameters in the service. I'm using this code to get data from Servie:

    nc.connect("http://localhost/project/public/service/gateway/amf");
    var res2:Responder = new Responder(returnDataList,returnError);             
    nc.call("Service_GatewayService.getData",res2);

But now i want to get data depended on an ID i send with the service. I've been testing what goes wrong and i've noticed that my 'sended' variabel always is null in Zend. I'm using the code on the Zend documentation like this. I want to send '1' as my id. The function in my service is working fine, the problem isn't there. I think he doesn't really send the variabel. This is the code i use

    nc.connect("http://localhost/project/public/service/gateway/amf");
    var res2:Responder = new Responder(returnDataList,returnError);
    var param:int = 2;          
nc.call("Service_GatewayService.getDataById",res2, param);

Someone know a solution for this...?

Thanks in advance