<?php include "Enum.inc"; abstract class Gender extends Enum { } class Female extends Gender { var $value = "f"; } class Male extends Gender { var $value = "m"; } var_dump(Gender::get("Male") === Male::get("Male")); var_dump(Enum::get("Male") instanceof Gender); var_dump(Enum::get("Male") instanceof Male); var_dump(Gender::get("Male") === Gender::get("Female")); var_dump(Gender::get("female"));