In my recent project, http://www.myflashlab.com/2010/01/27/contactform-class/ I was trying to do a lot of data transfer to and from flash to PHP (or any serverside script), I had to send attachments to php, I even had to encrypt the data before the transfer and that stuff. having to do all these things, I decided to write a class to take care of all these things for me.
so I wrote this fine class that I have named it FileSaver! 
This class is good for the following purposes:
- you want to save a file from your flash app to your desktop.
- you want to save a file from your flash app to your server.
- you want to save a file to your server and send some variables along with it.
- you want to send some variables to a server side script.
- you can encrypt the data before sending them out to server script.