AS3 Simple Post Request

var loader:URLLoader = new URLLoader();

var request:URLRequest = new URLRequest("/script.php");
request.method = URLRequestMethod.POST;

var variables:URLVariables = new URLVariables();
variables.key1 = "value1";
variables.key2 = "value2";
request.data = variables;

//Handlers
loader.addEventListener(Event.COMPLETE, onComplete);
loader.load(request);

private function on_complete(e:Event):void
{
    // whatever
}