Why Get Null Value?

<?php


class Person
{
    protected $name;

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

class Business
{
    protected $staff;

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

    public function hire(Person $person)
    {
        $this->staff->add($person);
    }

    public function getStaffMembers()
    {
        $this->staff->members();
    }
}

class Staff
{
    protected $members=[];

    public function __construct($members=[])
    {
        $this->members=$members;
    }

    public function add(Person $person)
    {
        $this->members=$person;
    }

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


$person=new Person('Sohel');

$staff=new Staff([$person]);

$business=new Business($staff);

$business->hire(new Person('ASad doee'));

var_dump($business->getStaffMembers());


?>