<?php

class Entity {

    private $type;

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

    public function getType() {
        return $this->type;
    }
}

class Animal extends Entity {

    public function __construct($type) {
        parent::__construct($type);
    }
}

class Dog extends Animal {

    private $tag;

    public function __construct($tag) {
        parent::__construct("Dog");
        $this->tag = $tag;
    }

    public function getTag() {
        return $this->tag;
    }
}

$dog = new Dog("Dog");
echo $dog->getTag();

?>