So I get the sense that PHP is sort of the tool of choice for web development at small or medium businesses which are not primarily software businesses, but are looking to create a website and maybe do some ecommerce? Is that right? If so I guess it makes sense that I wouldn't have seen it, most of my consulting work has been at relatively large enterprises.
Pretty much any shared hosting service (which is the default for a small business not going for a more handheld hosted solution like Squarespace or Shopify) is cPanel enabled with PHP, MySQL (via phpMyAdmin), one-click Wordpress installation, and other similar features.
It definitely feels that way, yes. I've mostly dealt with small businesses looking for the lowest bidder and medium businesses unable to spend a fortune on software licenses and highly-experienced devs, and PHP fits that segment well.
> [WordPress and] Drupal are immensely popular for simplistic sites
That's not a sentence I expected to see. Ever. Drupal is popular for many things but for simplistic sites?
This may be a regional thing. I've seen Drupal 6/7 on a lot of sites where the original dev threw together five content types in the admin GUI and told the admin how to post new content. It worked well and was certainly less worrisome than seeing (outdated) WordPress.
We run about 1,000 simple websites off the same Drupal codebase. Custom forms, page layouts, etc.
So your argument is that a multisite project running a thousand sites off the same codebase containing custom forms and layouts is simplistic? Then, I pray, what do you call complex?
PHP has its tentacles all over the web: WordPress and Drupal are immensely popular for simplistic sites and short-lived promotionals, Magento and WooCommerce attract many e-commerce users, and Symfony/Laravel handle the custom stuff. I've worked with all of these and have the scars to show for it.
All popular projects have swarms of consultants offering advice, prebuilt additions, and custom development. (E.g. WordPress plugins and themes are everywhere.) This is also a significant factor for the penny-pinching customer — from their point of view, they avoid vendor lock-in and expensive development this way. (Spoiler: it rarely works out, in the end. "Tower of Babylon" and "shallow learning curve" mix in very exciting ways.) So there are masses of people who know the basics of PHP and call themselves "PHP developers". In my opinion, just a fraction of them actually deserves that title.