AMFPHP is a Flash Remoting gateway for PHP. AMFPHP was the first open-source Remoting gateway and continues to be developed. Some distinguishing features of amfphp:
Flex RemoteObject and AMFPHP 1.9 Great getting started example of Flex2 and AMFPHP 1.9
Using Amfphp 1.9 with the Adobe Flex 2 SDK Another good example!