With Flash Remoting, you can call remote methods from the Flash client and the arguments will end up in the native remote language, and will come back to Flash correctly typed, so there's no messing with serialization at all.
AMFPHP is an open-source Flash Remoting gateway. It's fast, reliable, 100% free and open-source. Flash Remoting is a technology built into the Flash player core that enables sending data between the server and the client seemlessly. If you've built XML-based RIAs you know how much of a pain it can be to serialize the data, debug, and integrate into your application.
You can check out their site as well as a showcase featuring some of the sites that use the software...
