You only have to browse code on phpclasses.org (the most popular PHP code contribution site I think?) to see that there is something very very wrong with how PHP code is developed.
Also the comments left in the PHP documentation don't seem to be moderated on code quality and a lot of bad practice has slipped in.
To be fair, there are plenty of junk code sites out there. I'm amazed that http://www.codeproject.com still appears to be going strong.
Popular in that everyone knows its name and knows not to ever use it. It's an absolutely awful site that's been awful for an entire decade. Most of the code being uploaded there these days is from indian and brazilian developers.
All the good PHP libraries are on github and shared socially.
It really doesn't help PHP that a site as popular as phpclasses has such a large degree of inferior code.