[rmc]

Lots of massively popular sites use PHP, e.g. Facebook, Wikipedia.

I presume there's a lot of legacy code there.

[ihsw]

It was recently (2011) rewritten on top of Symfony2 -- http://symfony.com -- and more importantly a modern, documented, and stable framework. It was likely done because finding quality PHP programmers is easier than finding quality Perl programmers.

[culturestate]

When you say "it was rewritten...," which are you referring to?

[runevault]

except facebook wrote a compiler to get their PHP into c++ because it was too slow (but too much code to actually rewrite it).

[boyter]

Probably only because at their scale a 10% or even 5% reduction in the amount of servers equals millions of dollars a year.

For anyone with a handful of servers PHP is acceptable as the additional cost of 2-3 servers is not really that high.