Oddly enough in PHP the things I find most annoying aren't the inconsistent method names or parameter order. I can live with those as the documentation is pretty good and most IDE's give me a hint as to what its expecting.

The thing I find most annoying is being unable to pop the first element off an array when its returned and that when you do things like array_map it dosn't work with a method inside the same or other classes,

EG

$this->method()[0];

array_map($this->doSomething, $array);