Six years ago I wrote an large web application. It was my very first php program, and it grew, and grew. I used a lot of forms, and some very (atrocious) techniques to give an AJAX "look" to the site, and to handle multiple users with various permissions.

I am looking to expand this, and sell it to other companies in the field, but I need to seriously modernize it.

Currently, it loads index.php where you log in. The user can then select from various "students" or "participants" (We work with people with disabilities). From there, you can select different lesson plans or life skills that are being worked on. There are many other branches as well.

At each stage, a different page is served: Sel_Paricipant.php, Sel_Program.php, etc.

Are there any fundamental problems with doing it this way? If so, what are some good techniques for eliminating this, so that people only see the TLD in their address bar?

Thanks in advance. --Dave