[MichaelGG]

The engineers working on FB's PHP have reimplemented the runtime. I doubt that was a bonus or a reason they considered PHP. I find it highly unlikely anyone started off using a platform with the goal of "we get to completely re-implement this platform because it will not work for us otherwise."

[coldtea]

That's a flawed argument. The only reimplemented the runtime to get better performance, for their humongus needs. The PHP semantics and language remain the same.

So, them re-implementing the runtime is no more an argument against PHP than using PyPy instead of CPython or JRuby instead of MRuby is.

Not to mention that have they been using say Ruby instead of PHP, they'd have the same, or even worse, problems regarding getting the most performance out of their runtime.

So this is totally orthogonal to the issue of PHP's merits -- only has to do with performance, so the same things could have been said for Python or Ruby that are in the same ballpark as PHP in this area.