Reddit’s r/lolphp has some “great” memories of many of the shortcomings (most of which are historical now fortunately). My favorites are probably the randomly long and short function names, due to length being used for hashing, and DATE_8601 not being compatible with ISO-8601.

EDIT: Don’t want to start a flamewar, it really has improved over the years. Nonetheless, it has a less than bright past.