PHP is OK for small, short-lived web applications (which is, sometimes, exactly what you need). It's only when the small things outlive their original purpose age get large and complicated that maintenance becomes a nearly impossible job of fixing one thing without two others and when you really start regretting the choice of PHP.
Not that there is no nice, maintainable PHP code out there. It's just that the overwhelming majority of the PHP code I've seen is a broken mess.
Because PHP and the whole LAMP stack is like air. Everyone knows it because all you have to do to use it is just breathe. Anyone can just pick it up and immediately make an awesome website. It's a simple easy-to-learn language with dozens of easy all-in-one installers. No command line haxoring needed. Unlike ASP.NET, the tools are free. Unlike Rails or Django, hosting is cheap and easy to find.
With all the hate on PHP, I feel like it's the childhood friend from elementary and middle school that you out-grew because you became "too cool" for them in high school.
It's not like you can get a private VPS for next to nothing and, with things like Google App Engine (which supports Python and Java) going for almost nothing, there is little reason to go with PHP unless you have most of your code already written in it.
Does anyone not in the 'enterprise' or studying at University really love Java or C#?
They seem like very unlikely candidates for young self-taught programmers/designers imho.
When I started programming, I jumped into a lot of open source programs, poked them and cloned them just to understand how they worked.
There isn't really that much interesting open source C# / Java software at a basic level, and that I think might be the reason why self-taught programmers are more likely to use other languages.
General as in "shared by everyone" or as in "shared among geeks/nerds/people that are into development"?
Also interesting is their education, it's making it obvious that we are moving away from universities (although the sample isn't in any way big enough we can get the hint, I guess)