[flexcoders] Why Flex can not use flash.net.NetConnection?

[markflex2007]

 Hi,

 I have following code for amfphp.

 import flash.net.NetConnection; 
 private var connection:NetConnection;
 private var gateway:String = "amfphp/gateway.php";

 private function init():void
 {
    connection = new NetConnection();
    connection.connect( gateway );
              
 }

 .....

but I get error for "connection = new NetConnection();". the error is the 
following:
Unhandled NetStatusEvent:. level=error, code=NetConnection.Call.BadVersion

I know flash always use it,why flex can not use it?

Thanks

Mark