The big catch for you is your second question.

If I don't specifically exit() the script that gets the $dbh will the connect stay open?

You can maintain persistent connections to the database but you'll need a persistent process to manage them for you. I don't know much about Zeus. I think if you are dependent on your service provider for things like which server software will run, then developing this much complexity into your application is probably not a real option for you.

The good news is that you rarely really want to do what you are attempting anyway. The approach will tend to make your performance graphs look like a staircase because you are allocating resources to each user and tying those resources up even while the user is idle. With a good web application a user will only consume resources during an actual request at least as far as CPU and RAM go. (Disk usage is, of course, a different story.) Maintaining persistent DB connections makes the most sense in a case where users can share those connections.

The bad news is that you should probably bring your design back to the drawing board.

-sauoq
"My two cents aren't worth a dime.";