<?php X::$y = array(); X::$y[4] = 4; X::$y[44] = 44; X::$y[444] = 444; Y::$y = []; Y::$y[] = 5; Y::$y[] = 55; Y::$y[] = 555; Z::$y = array(); Z::$z[] = 5; Z::$z[] = 55; Z::$z[] = 555;