Sounds like a documentation problem, not one of the language.
You can shoot yourself in the foot with any programming language. PHP just happens to have one of the shallowest learning curves and greatest availability, so simply by virtue of being everywhere it's responsible for a lot of damage. It doesn't help that a newbie that came up with a working (but dangerous/incorrect/...) solution can then easily start answering other newbies' questions, although that's hardly a PHP-specific thing.
Further - because it's so many people's first programming language, they don't even know to look for information about best practices, let alone go out of their way for it. It takes a seasoned programmer to go out of his/her way to avoid repeating other people's mistakes.
Documentation and Community are a huge part of a languages usefulness. Every language that I consider to be well done has extremely good documentation and a Community that ensures that documentation is up to par.
The argument that community is not relevant to a languages usefulness is simply wrong. PHP suffers from poorer community than other languages. This is improving as the article highlights but it still has a long way to go.
PHP's documentation is some of the best I've encountered (which is quite important, as you have to use it all the time even after ten years because of all the bizarre function names and signatures on the early "core" code).
I completely agree about the community (I'm not sure who your comment is addressing, as I never argued that community is irrelevant, nor did the person to whom I was responding). But on the flip side - having some single pool of up-to-date knowledge is different than a circlejerk, and the "our way or the highway" attitude is very prevalent in some programming communities. Besides being incredibly alienating to newbies, it actively holds back development of new features and discussion of new ideas because these community managers are not trying to solve the same set of problems as the developers using the language/framework.
Yes, it's a damn shame that plenty of PHP example code is from 2006 and still sitting at the top of Google - but by and large, it still works just fine and has accurate information. It may be doing messy stuff like mysql_real_escape_string instead of prepared statements, but the end result is the same.
All of the community and documentation in the world won't stop people from using the tools wrong, and if you take away all the potentially-dangerous tools, you're left with very few things that are actually useful. I'll reiterate my previous point here: something with a low barrier to entry will tend to attract novices, and novices tend to make a lot more mess than seasoned practitioners. If PHP didn't exist and Python or Ruby took its place as the easiest thing to get up and running with, most (no, not all - I've worked with PHP long enough to know which ones are genuinely PHP-specific, and it's not many) of these PHP-hate comments could be run through s/PHP/NEWLANG/g and be completely accurate. Even when you start looking for best practices on a new language you'll encounter a valid counterexample for every single one of them, since it depends on what you're doing.
You can shoot yourself in the foot with any programming language. PHP just happens to have one of the shallowest learning curves and greatest availability, so simply by virtue of being everywhere it's responsible for a lot of damage. It doesn't help that a newbie that came up with a working (but dangerous/incorrect/...) solution can then easily start answering other newbies' questions, although that's hardly a PHP-specific thing.
Further - because it's so many people's first programming language, they don't even know to look for information about best practices, let alone go out of their way for it. It takes a seasoned programmer to go out of his/her way to avoid repeating other people's mistakes.