Summary
Developing modules in Drupal is an important way to solve the 80/20 rule and to contribute back to the community. Drupal has a robust framework that allows for modules to extend out of the box Drupal and observe standard conventions that all modules follow. Modules often make use of patterns in both Symfony and Drupal. Modules have defined best practices across configuration, PHP code, and more through constructs such as the composer.json file, automated tests, and more.
The next chapter explores theme development in Drupal, important for the visual styling of a Drupal application.
