In this new blog post, Mike Potter points out two examples of the AMFPHP package in action as provided by Renaun Erickson.
The source code to both examples is available as well. (You did know that Flex applications have the option of publishing the source code right? [...] To publish the source code for your own application, in Flex Builder select Project -> Publish Application Source...)
He also mentions an upcoming update to the PHP RIA SDK by Adobe to include some of these sorts of examples. Check out the mailing list for more.