Description:
------------
---
From manual page: https://php.net/language.oop5.variance
---

in the Contravariance section there is :

abstract class Animal
{
    protected string $name;

    public function __construct(string $name)
    {
        $this->name = $name;
    }

    public function eat(AnimalFood $food)
    {
        echo $this->name . " eats " . get_class($food);
    }
}


The eat method should instead take Food as a type hint, and not AnimalFood.

i.e. something more like :

abstract class Animal
{
    .....
    public function eat(Food $food)
    {
        echo $this->name . " eats " . get_class($food);
    }
}




Test script:
---------------
<?php

abstract class Animal
{
    protected $name;

    public function __construct(string $name)
    {
        $this->name = $name;
    }

    abstract public function speak();


    public function eat(AnimalFood $food)
    {
        echo $this->name . " eats " . get_class($food);
    }
}

class Dog extends Animal
{
    public function speak()
    {
        echo $this->name . " barks";
    }
}

class Cat extends Animal 
{
    public function speak()
    {
        echo $this->name . " meows";
    }

}



interface AnimalShelter
{
    public function adopt(string $name): Animal;
}

class CatShelter implements AnimalShelter
{
    public function adopt(string $name): Cat // instead of returning class type Animal, it can return class type Cat
    {
        return new Cat($name);
    }
}

class DogShelter implements AnimalShelter
{
    public function adopt(string $name): Dog // instead of returning class type Animal, it can return class type Dog
    {
        return new Dog($name);
    }
}

class Food {}

class AnimalFood extends Food {}

$kitty = (new CatShelter)->adopt("Ricky");
$catFood = new AnimalFood();
$kitty->eat($catFood);
echo "\n";

$doggy = (new DogShelter)->adopt("Mavrick");
$banana = new Food();
$doggy->eat($banana);


Expected result:
----------------
Ricky eats AnimalFood
Mavrick eats Food

Actual result:
--------------
david@walnut:~/src/php-library/animals$ php7.4 animals.php 

Ricky eats AnimalFood
PHP Fatal error:  Uncaught TypeError: Argument 1 passed to Animal::eat() must be an instance of AnimalFood, instance of Food given, called in /home/david/src/php-library/animals/animals.php on line 75 and defined in /home/david/src/php-library/animals/animals.php:15
Stack trace:
#0 /home/david/src/php-library/animals/animals.php(75): Animal->eat()
#1 {main}
  thrown in /home/david/src/php-library/animals/animals.php on line 15