Drupal is written in the PHP programming language. PHP is a widely supported, multiplatform, and web-centric scripting language. Since Drupal is written in PHP, this book will largely feature code written in PHP, albeit with Drupal standard practices being kept in mind.
It is very important to note that the minimum version of PHP required for Drupal 8 to run (and install via Composer) is 5.5.9. Moreover, since the current version of PHP (at the time of writing this book) is PHP 7, I personally recommend that you run Drupal 8. It's best to start off right.
Regarding the style of PHP, a very important change compared to Drupal 7 is the heavy use of object-oriented code and design patterns. Granted, many procedural style approaches remain ...
