<?php
class ๐Ÿ–pig {}
class ๐Ÿ—boar extends ๐Ÿ– {}

class Asterix
{
    public function hunt(๐Ÿ–pig $animal) {}
}

class Gauls extends Asterix
{
    public function hunt(๐Ÿ—boar $animal) {}
}
?>
Warning: Declaration of Gauls::hunt(๐Ÿ—boar $animal) should be compatible with Asterix::hunt(๐Ÿ–pig $animal)



Arguments types are contra-variant: