Summary
The Drupal theming system is complex and flexible and thus impossible to cover fully in one chapter of a module development book. However, we did go through the basics necessary to get you started—understanding the core tenets of the theme system, some of its most important Drupal specificities and practical use cases.
We started this chapter by discussing the abstract principle of separating business from presentation logic—a principle that is used by many modern web applications. We saw why it is critical for flexible and dynamic theming. Next, we discussed a great deal about how Drupal does this separation—the mighty theme hooks that act as a bridge between the two layers. Here, we also covered some of the highly used practices surrounding them—preprocessor functions and theme hook suggestions for added flexibility. Then, we covered how the business logic can actually use theme hooks—the render arrays (perhaps one of the most important...