Outside of the wide availability of PHP servers for cheap, what makes PHP so great for beginners? With Ruby, Python, Go, hell, even JSP for the "instant", in-HTML effect, I just don't see PHP as some gloriously "easy" language to use.
On top of it, there are hundreds of thousands of PHP tutorials all across the Internet that just have poor, poor, poor suggestions and design patterns that lead to people storing passwords unhashed, or unsalted. Sure, it's not unique to PHP, but it's really, really easy to get wrong in PHP and that's painful for a beginner and it's hard to progress and mature as a PHP developer without an existing code base to learn from.
tl;dr: I'm not convinced is as great as many here make it out to be. (To note, the first thing I sold was written in PHP in highschool. Since then I've used JSP/J2EE stack/python/ruby and now am infatuated with Go, so my opinion is not simply based on group-hate for PHP)