WordPress and Drupal are both very popular Content Management Systems (CMS) that power large parts of the internet. The two projects share quite a few things. They were started early in the 2000's and have grown to be large players in a market that used to be owned by Proprietary Software.
For the longest time these two tools were technically identical, built with the LAMP platform with Linux, Apache, MySQL and PHP. There are variations of these, but both Drupal and WordPress could be ran in the same environment. This was the status a year ago, but since that there has been significant steps in the two projects diverging technically.
Drupal 8 was launched late in 2015 and with heavy investment in modernisation of their core platform in the PHP language. The Drupal project remains deeply entrenched in PHP for their backend. This is natural after just spending years of time to rewrite parts of their platform.
Time will show how the projects will evolve. While PHP is considered by many to be a stale and boring language, the Symfony components and contemporary programming conventions have a proven track record of providing real world solutions. PHP maybe verbose and Java-like, but it certainly delivers for old time Drupal developers.
While Drupal 8 is finally gaining acceptance among the developer circles, the JS heavy WordPress stack of the future will without a doubt be a shocker for many WordPress used to hacking around in procedural PHP. What is sure is that the 2026 in the comic below, will be quite different from 2016 - even if the brands remain the same: