polymorphism in php

interface IAnimal
{
function getName();
function talk();
}

abstract class AnimalBase implements IAnimal
{
protected $name;

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

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

class Cat extends AnimalBase
{

public function talk()
{
return "Meowww!";
}
}

class Dog extends AnimalBase
{

public function talk()
{
return "Arf! Arf!";
}
}

$animals = array(
new Cat("Missy"),
new Cat("Mr. Mistoffelees"),
new Dog("Lassie")
);

foreach ($animals as $animal) {
echo $animal->getName() . ": " . $animal->talk();
}

?>

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