Maybe I should have expressed myself more clearly: The comment I replied to seemed to indicate that PHP must be bad since Facebook had a need to change it. My point was that, given the fact that Facebook has way more users than other sites and mostly serves non-cacheable pages, their needs are different than the needs of 99.9999% of other sites in the world, so the fact that they were forced to change PHP doesn't say anything about PHP's quality as a language.
The # of users really says nothing about how expressive the language you're programming in is.
And if we're talking about consumer products like facebook, it doesn't even say anything about how fast your programming language is since performance is dominated by database access time.
At best, we can try and claim that Facebook found PHP to be insufficiently expressive/safe/suited for them once they had X number engineers making Y number of changes per day.
Maybe they really could "move fast and break stuff" with 200+ engineers trying to commit to a vanilla PHP codebase.
