I don’t believe that 78% of websites run on PHP
Its a "fact" PHP devs love. The truth is 95% of PHP is not actaully PHP, bit wordpress/drupal and the other cms's.
Its click, drag, click drag and the underlying tech has zero importance really.
78% of websites where it can be deduced from client side code what server side tech is used. W3tech published this statistic, and the whole community picked it up while ignoring that very important caveat.
Not a very meaningful statistic.
Anyone who cafés about security would stay away from PHP. Certainly more than 22% of the web.
They're counting wordpress, drupal, various forums, etc. They make up a huge percentage of custom sites.
If you're talking only custom built stacks, the percentage is definitely lower, but probably still surprisingly high.