$menu = array(
    0 => array(
        array('id' => 1, 'parent_id' => 0, 'title' => 'First level #1'),
        array('id' => 2, 'parent_id' => 0, 'title' => 'First level #2'),
        array('id' => 3, 'parent_id' => 0, 'title' => 'First level #3'),
    ),
    1 => array(
        array('id' => 8, 'parent_id' => 2, 'title' => 'Second level #8'),
    ),
    2 => array(
        array('id' => 4, 'parent_id' => 2, 'title' => 'Second level #4'),
        array('id' => 5, 'parent_id' => 2, 'title' => 'Second level #5'),
    ),
    4 => array(
        array('id' => 6, 'parent_id' => 4, 'title' => 'Third level #6'),
        array('id' => 7, 'parent_id' => 4, 'title' => 'Third level #7'),
    ),
);