This script is part of a correction of the application built in this tutorial. Improvements include: * Unobtrusive JavaScript (Users with JavaScript disabled can still use the application.); * Modular PHP and JavaScript (They aren't intertwined, so the JavaScript could be used with, for example, ASP.); * Separation of logic and layout (No HTML event-handlers are used.); * Configurability (Any number of database/dropdown pairs may be used without significant modification, and the existing names are easily changed.); * Reliable URLs (They may be freely exchanged between users with and without JavaScript enabled and the page will still work.).