CMS Drupal has been written in PHP keeping in mind the simplicity and affordability of the scripting language. PHP is extensively accessible to amateurs and at the same time extremely efficient and loved by professional developers too. Almost every Internet Service Provider (ISP) supports PHP which makes it easier for your Drupal website to go live!
PHP has definitely evolved over the years. A lot of changes have been made over the years especially since version 5 making it more effective in writing fine code and using it in larger projects. The object-oriented model was also revamped after the 5th version and everything you need from object-oriented programming features are now available to use.