Developing a quiz application with server side and AJAX?

Hello Experts,

I need to write a quiz application which would have about 15 chapters for user(s) to go through. I already have done this application in FLASH AS3, and it gets the job done, but I had to employ AMFPHP as middle-ware to facilitate server side interaction with FLASH. The current platform for this applications consist of:

PHP, AMFPHP, MYSQL, FLAHS AS3

I am now thinking about writing this very application in either .Net or J2EE. But I would like to employ JQUERY with AJAX / AJAX JQUERY PLUGINS. I would like to know if this would be a good path to consider. With my current application which is done in AS3, I have encountered certain shortcomings such as:

I cannot run sessions
Security is not very tight
Flash does the user authentication and php handles the dynamic data, I would like to have PHP does the authentication and handle the dynamic data whereas Flash would just handle the presentation layer which will then require communication between the flash player and the browser.

I apologies for such long-winded  question, but I want to make sure you understand all of my concerns. I would highly appreciate you thoughts on this. I would like to know if you would handle this application via my proposed server-side solutions?

Thanks alot.