With the argument ordering stuff, they could just do what they did with microtime() where they added the extra argument so you could call microtime(true) instead of that list($sec, $usec) = microtime() crap.

Can't remember one of the backwards ones off the top of my head, but using in_array as an example,
bool in_array ( mixed $needle, array $haystack [, bool $strict] )
can become
bool in_array ( mixed $needle, array $haystack [, bool $strict, bool $swapNeedleAndHaystack] )

and a PHP warning can be raised if you don't pass the $swapNeedleAndHaystack argument warning that functionality for this method will switch in PHP 7 and will throw an error if it isn't passed, then in PHP 8 it can be removed entirely so it looks like this:
bool in_array ( mixed $haystack, array $needle [, bool $strict] )

Again, I'm not sure if in_array() is one of the backwards ones and I can't think of one off the top of my head, it's just an example.

Has the loudness war done all the damage it can do? That did a lot more to make things sound like ass than mp3 (and made mp3's job harder).