This is precisely the case. Most big sites would move away form PHP but they have so much technical inertia in it that it would be too costly so they instead ex

This is precisely the case. Most big sites would move away form PHP but they have so much technical inertia in it that it would be too costly so they instead extend it in new and novel ways. Facebook hit a wall with what they could make Facebook do so they essentially wrote a parser that translated it to C++. Other companies have one off C extensions still other companies just have lots of hardware to throw at it. There is still a problem with the language, in that once you get to its limits ( which you reach quickly ) then you are stuck between re-architecting your system or basically ripping out the internals of the language and replacing them with your own bits. tl;dr Friends don't let friends write projects in PHP