This. PHP's "==" is yet another trap of incompetent language design and almost all code that ever used it does the wrong thing for some inputs. $x == $y && $y =

This. PHP's "==" is yet another trap of incompetent language design and almost all code that ever used it does the wrong thing for some inputs. $x == $y && $y == $z doesn't even tell you that $x == $z, much less that $a[$x] == $a[$y].