This final chapter includes three sets of scripts that implement common features on many content-based websites: a voting system, an electronic card service, and a blog. These are all just starting points. Although they certainly work as presented, to use them in production, you will want to adapt them to your own needs and fit them to your security model.
All of these projects use MySQL to store data. The table structure and queries here are somewhat more complicated than what you've seen so far in the book, but it's not a big leap. Each system has its own set of tables, and you'll see how to create them.