This is the best point in this thread, IMHO.
I think it also is due to the fact that PHP is a fairly easy language for a non-coder to pick up little-by-little. One can easily start using it for doing simple things, like injecting dynamic data into a web page. From there one can learn to scale up to full web apps.
I think this lower barrier of entry makes a lot of developers feel insecure. A lot of coders think they are blessed with some sort of special ability to write code. They seem themselves as elite and they use elite tools. When some kid comes in with some PHP snippets and generates a lot of value from that they complain that their code sucks, the language sucks, the developers suck, blah blah.
In my 20 years of writing code (starting with PHP) I have learned the lesson over and over again that while writing code commercially the fact that the language has feature X or that it forces certain patterns means almost nothing. Sure, your developers might feel better about themselves but that is about it.