flash app to retrieve variables from an externally called local php page

Hey all, i have a problem. :)
I require my flash app to retrieve variables from an externally called local php page. How it works is my flash app calls my payment gateway in a new browser window, payment steps are followed by the client and the payment gateway then refers the client to a copnfirmation or declined page on my server, i require my flash app to retrieve variable from those pages depending on which is called. I know how to send and get variables from and to php pages but only if it is called by flash. how do i get variables from these pages?
thanks

Anthony.