note 125704 added to language.oop5.variance

Following the examples above, you might assume the following would be possible. <?php class CatFood extends AnimalFood { ... } class Cat extends Animal { public function eat(CatFood $food) { echo $this->name . " eats " . get_class($food); } } ?> However, the Liskov Substitution Prinicpal, and therefore PHP, forbids this. There's no way for cats to eat cat food, if animals are defined as eating animal food. There are a large number of legitimate abstractions that are forbidden by PHP, due to this restriction. ---- Server IP: 45.112.84.4 Probable Submitter: 45.91.159.166 (proxied: 212.69.47.82) ---- Manual Page -- http://php.net/manual/en/language.oop5.variance.php Edit -- https://master.php.net/note/edit/125704 Del: integrated -- https://master.php.net/note/delete/125704/integrated Del: useless -- https://master.php.net/note/delete/125704/useless Del: bad code -- https://master.php.net/note/delete/125704/bad+code Del: spam -- https://master.php.net/note/delete/125704/spam Del: non-english -- https://master.php.net/note/delete/125704/non-english Del: in docs -- https://master.php.net/note/delete/125704/in+docs Del: other reasons-- https://master.php.net/note/delete/125704 Reject -- https://master.php.net/note/reject/125704 Search -- https://master.php.net/manage/user-notes.php