AMFPHP

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.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.

You also get to use the wonderful NetConnection debugger, which shows you exactly what's being sent between the client and server. Remoting uses AMF, a very lightweight binary format that cuts the bulk out of packets, meaning data exchange is a lot faster than with XML. All in all, Remoting is the way to go if you're looking to build robust, fast and secure Rich Internet Applications.

AMFPHP is a complete implementation of Remoting for PHP with tons of features built-in to make creating Remoting apps a whole lot simpler. A distinguishing feature of AMFPHP is the built-in service browser, which you can test out live here, which makes testing asynchronous apps and generating stub code a click away. You can read more about why AMFPHP and Remoting rock. Or read more about the AMFPHP project.

from: http://www.amfphp.org