Beginning Drupal 8

Chapter 12 ■ Anatomy of a Module
Step 5: Create the Module’s Controller
Drupal 8 follows Symfony’s and PHP 5’s object orientation approach. One of the key concepts that Drupal
8 has adopted is a standard called PSR-4, which defines how code is loaded into memory. One of the issues
with previous versions of Drupal is that a lot of code is loaded into memory when it doesn’t need to be there.
PSR-4 solves that issue, and one of the enablers is something called namespaces. In our routing file, the value
associated with _content starts with \Drupal\hello\Controller, which is a namespace. PSR-4 defines
that a namespace maps directly to the file structure of your application. Symfony requires that all of our
namespace directories reside within a directory named src, which resides in the root directory
of our module.
So let’s get busy and create the directories where the next component of our module will reside, the
controller. While in the root directory of our hello module, create a new directory named src, and within
the src directory, create a new directory named Controller. Within the Controller directory, we’re now ready
to create the controller for our application, the “traffic cop” of our application. In your favorite text editor,
create a file named HelloController.php. The contents of our controller should be