"You simply cannot run a top-level Internet business on PHP anymore" - I guess you mean ONLY on PHP. Maybe Facebook is not using just PHP... Twitter and Slides

"You simply cannot run a top-level Internet business on PHP anymore" - I guess you mean ONLY on PHP. Maybe Facebook is not using just PHP... Twitter and Slideshare demonstrated that you cannot run their businesses exclusively with Ruby on Rail. Pinterest and Quora have done the same with Python. At a certain scale, it is more economical and efficient to optimize part of your architecture with services written in other languages. This has always be true. People has massively relay on caches that are usually written C/C++ Ex: memcache is a very tiny piece of C has been used with PHP, Python, Ruby forever. However you would be surprised to know how many million dollar businesses are running almost exclusively on PHP. I am not saying that is the best choice, but it is the reality.