Null Problem

<?php

class Person
{
    public $name;

    public function __construct($name)
    {
        var_dump('Hello!! '.$name);
    }
}

class Man
{
    public $age;

    public function add(Person $age)
    {
        var_dump('This is oKay');
    }
}

$person=new Person('Rasel');

$man=new Man();

var_dump($man->add($person));