Straight from their website:
PHPObject is an opensource alternative to Flash Remoting for PHP developers. With PHPObject, you can call a method of a PHP class/library on your web server as if the class/library was defined in Flash itself. It takes care of your client-server connections and makes passing of variables (properties) between Flash MX and PHP easy, and thereby providing a convenient way to connect rich media clients with data and business logic residing on your server.
Sounds pretty useful… Here’s the link: PHPObject