[lukifer]

In addition to the oft-cited deployment story, I think another reason for PHP's success is that it's the only major language specifically created as a DSL for rendering web pages. Once you're accustomed to having its baked-in toolset for web-related tasks, having to constantly hunt for the right third-party library in a general-purpose language like Ruby or Python becomes a major drag coefficient, even if those languages are objectively better in all other respects.

[dkuntz2]

What features are built in to PHP that aren't built in to Ruby and Python?

This is actual curiosity, I just can't think of anything that PHP has that Ruby and Python don't. Even more so when it comes to Go. But you didn't mention Go.