It’s still popular af. Almost half of any cms site online is powered by Wordpress. Many sales sites use woocommerce (Wordpress plugin). Message boards for sure (phpbb!). Moodle and other similar learning management tools run on PHP. Other cms systems like drupal and joomla make up another big portion of cms installs. I think the custom Wikipedia (mediawiki?) is php.

I just got a nostalgia hit remembering all the phpBB type boards.

But also I haven’t seen much of that style of bulletin boards in ages. Maybe the occasional EEVBlog or Ars kinda count?

It's still the most widely used server side language on the web thanks to WordPress, unless that has changed recently (it was dropping)

Facebook is developed on a reimplementation of PHP!