Eric Ries – Why PHP won:

"Everything is request-oriented, short-lived, and stateless. A PHP script is like an object itself, encapsulating a bit of functionality behind an interface defined by HTTP. It's one of the most effective paradigms for software devlopment in history. The platforms that win on the web are those that mirror its fundamental structure, not those that try to morph it into a more traditional "elegant" shape.

[…] For them, PHP is an ideal language precisely because it gets out of their way, allowing them to build a simple foundation for their complex and beautiful browser-based cathedrals."