I just don't understand the hate. Like any language it has some syntactic quirks and inconsistencies. There's no way to objectively say that one language is superior to another, because there are so many metrics that contribute to superiority and every person in the world is going to weight those various metrics slightly differently.
I imagine it's neither "despite" nor "because" of PHP use; any top-tier developer is going to use the tools available to him/her, rather than pick an employer in order to use a specific set of tools. Lower-quality developers may do so, but that's probably because they're less likely to know the right tool for the job (eg someone may hate functional programming and avoid jobs that use it, but that's because they don't know when FP is the ideal way to solve the problem)
You can't objectively say that one language is better than another, but you can't deny that a language such as Haskell has a level of consistency and mathematical rigour that PHP will now never attain. Top developers who Facebook target (normally top CS students from top colleges and PhD programs) strive to be consistent and mathematically rigorous themselves, and poor design and math annoy them.
Totally valid point. One of my housemates loves Haskell for very much the same reasons, and all other things being equal I'd prefer that as well (who wouldn't?).
But of course, anyone who's worked on production systems knows that all the mathematical ideals in the world doesn't stop bugfixes from becoming a giant hairy mess. It's more your culture, skill, and process that allow or prevent that from getting refactored into a better solution and how long that takes. Any language can be a part of a clean or messy codebase, although some tend to skew towards one side or another - but I'd wager that's as much a factor of barrier to entry as anything else.
I imagine it's neither "despite" nor "because" of PHP use; any top-tier developer is going to use the tools available to him/her, rather than pick an employer in order to use a specific set of tools. Lower-quality developers may do so, but that's probably because they're less likely to know the right tool for the job (eg someone may hate functional programming and avoid jobs that use it, but that's because they don't know when FP is the ideal way to solve the problem)