Animal

prey()

abstract class Animal {
    // child classes must implement this
    abstract function prey();

    public function run() {
        echo "I am running!\n";
    }
}

class Dog extends Animal {
    public function prey() {
        echo "I killed the cat !\n";
    }
}

class Cat extends Animal {
    public function prey() {
        echo "I killed the rat !\n";
    }
}

$dog = new Dog();
$cat = new Cat();

$dog->prey(); // I killed the cat !
$cat->prey(); // I killed the rat !

$dog->run(); // I am running!
$cat->run(); // I am running!