Drupal just celebrated a major milestone - its fifteenth birthday!
The Drupal project has grown tremendously over the years and with Drupal 8 it is now 'off the island'. Since its early days, Drupal has held on to its own internal ways of coding and using PHP, but with Drupal 8 this change changed dramatically. Now Drupal uses Composer, OOP, Twig, YAML, and Services to name a few. This new policy of openness will help Drupal grow and improve. It will allow themers to do their thing and coders to do theirs - better than before.