Polymorphism Using Abstract Classes in PHP OOP

<?php

abstract class Animal
{
    protected $name;

    public function getName()
    {
        return $this->name;
    }

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

    abstract public function sound();
}

class Cat extends Animal
{
    public function __construct($name)
    {
        $this->name = $name;
    }

    public function sound()
    {
        echo $this->name . ' sound meow<br>';
    }
}

class Dog extends Animal
{
    public function __construct($name)
    {
        $this->name = $name;
    }

    public function sound()
    {
        echo $this->name . ' sound woof<br>';
    }
}

class Horse extends Animal
{
    public function __construct($name)
    {
        $this->name = $name;
    }

    public function sound()
    {
        echo $this->name . ' sound neigh<br>';
    }
}

$cat1 = new Cat('Cat 1');
$cat2 = new Cat('Cat 2');
$dog1 = new Dog('Dog 1');
$dog2 = new Dog('Dog 2');
$horse1 = new Horse('Horse 1');
$horse2 = new Horse('Horse 2');
$animals = [$cat1, $dog1, $horse1, $cat2, $dog2, $horse2];

foreach ($animals as $animal) {
    $animal->sound();
}

?>

Output

Cat 1 sound meow
Dog 1 sound woof
Horse 1 sound neigh
Cat 2 sound meow
Dog 2 sound woof
Horse 2 sound neigh