Эдвард

$class = new Child;
$class->set('test');
echo $class->get();

<div id="diver"></div>
<div id="diver"></div>

<div class="diver"></div>
<div class="diver"></div>

class MySQL
{
    public function connect()
    {
        // code...
    }
}

class Page 
{
    protected $mysql = null;

    public function __constuct()
    {
        $this->mysql = new MySQL;
    }

    public function view($id)
    {
        $this->mysql->where($id);
    }

    public function delete($id)
    {
        $this->mysql->delete($id);
    }
}

$page = new Page;
$page->view($id);
$page->delete($id);