>Besides inconsistent/bad library argument order/naming
These issues are the least of it's 'quirks'. The most important thing that is wrong with it is the badly or 'un-designed' core of the language. This result of this is that when you are implementing modern programming constructs, you won't be able to implement it in a consistent way (Most of the time the implementers does not care, but even if you do you ill see quickly running out of options.). So the modern features PHP get are often half-baked so that if you try to put it to real use, it ll come to a grinding halt.
Another aspect of this 'un-designed' core is that there will be a big fight over introduction of any 'core-like' feature. And often implementers wont be able to go with one philosophy and is forced to make everyone happy, ending up with very weird behaviors in the implementation.
Another thing is Exceptions. Because the exceptions was not available from the start, only a part of the language uses them. So you cannot rely on exceptions being thrown in a consistent way.
Another important thing is the most people who have been working on the language are hobbists and students with no sort of professional experience, and they end up implementing the features in the most awkward fashion (Eg: Methods on the datetime object mutating it).
One could go on and on and on..http://www.reddit.com/r/lolphp