Craziest part is it was never even intended to be a programming language. From the Wikipedia page, the founder Rasmus Lerdorf is quoted as saying:

"I don't know how to stop it [...] there was never any intent to write a programming language [...] I have absolutely no idea how to write a programming language [...] I just kept adding the next logical step on the way."

And 23 years later here we are with php2shell and it powering 70% of the internet’s websites