We have just finished the last module of the book, and it was a big one. In this chapter, we covered several important Drupal APIs and subsystems. Notably, we created filters, an input format, an action, and a new hook. We also revisited the mail subsystem and used themes to create email-friendly content.

Five modules and two themes—that's what we've created so far. To close the book, though, we are going to leave module development and look at another advanced programming feature of Drupal: Installation Profiles. We will create our own installer, which will install the Drupal core system and our theme and five modules.