This contribution comes from the inspiration of Jason D. Agostoni who presented his code in an article on "Security and Sessions in PHP". His article and documentation can be found at:
I was concerned if this code would conflict with the Admin session ID: osCAdminID. In all of my testing I have not experienced any problems with it at all.
One major security problem that we needed to solve is that anyone can use the backspace button on their browser to get back into secure areas on many web sites after logoff. We have merchants using their shopping carts in their stores where security is important from customers and other employees.