sending variables to active flash movie

I have a webpage with two frames, the swf in the left and the php page in the right. i need to send a variable to the swf so that future url calls from the swf are encoded with specific variables. Basically I need the swf to load different variables depending on the variables it is sent.

Can this be done. I can do it with sessions and just get flash to call a generic page and include different files by calling session variables. The problem is I cant carry variables via URL encoding because the flow is:

Load PHP page>load next page from Flash (this page needs to load from variables sent from the initial php page)

Thanks