<?php class MY_BASE { public static $x = 3; } trait MY_TRAIT { public static $x = 3; } class MY_CLASS extends MY_BASE { use MY_TRAIT; public function printX() { var_dump(self::$x); self::$x = 4; } } $o = new MY_CLASS(); $o->printX(); var_dump(MY_BASE::$x); var_dump(MY_CLASS::$x);