Yes. We use PHP and we love it! It has its, er, quirks from time to time, but allll that negative stuff that you're always reading about PHP doesn't really affect the bottom line: PHP is great at building websites and scalable web apps, warts and all.

(Edit: a few others in this thread are observing that most PHP-ers got their start in the early 2000's. To add another datapoint, that's true in my case as well. Active since 1998, I started with perl, got familiar with PHP, moved on to MS tech for a few years, then became a RoR dev in ~2005-07. Eventually I got frustrated with Rails' performance, decided to refactor an app in PHP and was blown away by the two-orders-of-magnitude performance difference at the time. I've stuck with PHP since then, though I still play with Node and Python. All great tools. I hate the language wars, use whatever works for you.)

As an anecdote - in my circles I observe that PHP is very popular among people who started working in web ~2000, while ruby is popular among those who started in ~2007. Nothing to do with seniority etc, I think it's simply the default choice of whatever was in vogue at the time when the person started hacking, and by now many PHP guys skew older and are out of the startup game (i.e. working in established companies on established products).

As another example, I'm still astonishingly productive with PHP for backend APIs and rapid development projects. The symfony/Doctrine community has done a phenomenal job at bringing world-class tools to the language.

Pure conjecture, use salt liberally: PHP was 'in vogue' in 1998 to the mid 00's, after that a ton of other (and better) options appeared (I say that as a 'PHP guy'). So if you look at younger people you're likely not going to find a very large number of programmers there that will have PHP as their first language of choice. The older ones though might find that their experience with that particular platform will give them an edge over first learning a new stack.

So to complete the guess I think if you focus on the teams with older technical founders you might find some PHP but in the teams with younger technical founders I doubt that that would have a high incidence.

Laravel is indeed the thing I am learning next from PHP, and I love the Startup ecosystem (and working in one), so I guess I'm not the only one. Also, take into account different countries; I'm from Spain and the Rails ecosystem is really weak here.

Mailchimp is 100% PHP.

Probably only with things such as Laravel, but I guess it's frowned upon.