organization รบกวนผู้รู้ช่วย code ด้วยครับ ต้องการหาสาย up , down ของตำแหน่ง

Array
(
    [0] => Array
        (
            [id] => 15
            [name] => abc
        )

    [1] => Array
        (
            [id] => 16
            [name] => abce
            [part] => Array
                (
                    [0] => Array
                        (
                            [id] => 17
                            [name] => abc
                            [part] => Array
                                (
                                    [0] => Array
                                        (
                                            [id] => 61
                                            [name] => b
                                        )

                                )

                        )

                    [1] => Array
                        (
                            [id] => 60
                            [name] => a
                        )

                )

        )

)

id  parernt_id  position_name
5	0	President
18	1	AC Sup
8	2	Engineer Sup
1	5	Admin Mng
2	5	Sale Mng
9	5	Worker
59	5	General Manager Management
3	8	HR
14	9	Junior Sup
15	14	abc
16	14	abce
17	16	abc
60	16	a
61	17	b

$position_down = array();
		foreach($result as $val){
			$position_down[] = $val['id'];	
			if($val['part']){
				if(!empty($val['part'])){
					for($i=0;$i<count($val['part']);$i++){
						$position_down[] = $val['part'][$i]['id'];		
					}
				}
			}
		} 
		
		echo 'id Down';
		echo '<pre>';
		print_r($position_down);
		echo '</pre>';

//แสดงยังไม่ครบ
id Down
Array
(
    [0] => 15
    [1] => 16
    [2] => 17
    [3] => 60
)