The DevX.com site has posted some code that gives you methods for passing information back and forth between PHP and a Flash application.

When you need to develop a web form with a special design and great effects, you will probably elect to use Flash. But building and programming Flash forms is considerably different from building standard HTML-based forms. [...] To do that though, you need to know how to access data in the Flash form and (sometimes) how to update the Flash form from PHP as well.

They help you build a sample Flash form as a base to work with in the transfer methods including the ActionScript to get the data out of each field. The tutorial shows the two way communication that's possible - pushing the Flash values out to the PHP script via a getURL() call and pulling the results back in with a call to loadVars() from the PHP script's output.