数组重组,该怎么处理

#原数组

$list = array(

	0=>array('mid'=>1,'menu'=>'m1','level'=>1,'belong'=>0,'higher'=>'a1'),

	1=>array('mid'=>1,'menu'=>'m1','level'=>1,'belong'=>0,'higher'=>'a2'),

	2=>array('mid'=>1,'menu'=>'m1','level'=>1,'belong'=>0,'higher'=>'a3'),

	3=>array('mid'=>2,'menu'=>'m2','level'=>1,'belong'=>0,'higher'=>' '),

	4=>array('mid'=>3,'menu'=>'m3','level'=>1,'belong'=>0,'higher'=>' '),

	5=>array('mid'=>4,'menu'=>'m4','level'=>1,'belong'=>0,'higher'=>'d1'),

	6=>array('mid'=>5,'menu'=>'m5','level'=>1,'belong'=>0,'higher'=>'e1'),

	7=>array('mid'=>5,'menu'=>'m5','level'=>1,'belong'=>0,'higher'=>'e2')

	);

#从原数组中提取新数组

$menuArr = array(

	0=>array('mid'=>1,'main'=>'m1','child'=>array('a1','a2','a3') ),

	1=>array('mid'=>2,'main'=>'m2','child'=>' ',

	2=>array('mid'=>3,'main'=>'m3','child'=>' ',

	3=>array('mid'=>4,'main'=>'m4','child'=>array('d1') ),

	4=>array('mid'=>5,'main'=>'m5','child'=>array('e1','e2') ),

);

#自己搞半天搞晕了：

$sign = null;

$n = 0;

$menuArr = array();

foreach($list as $men){

	if($sign == $men['mid']){

		echo "n:{$n}<br>";

		$menuArr[$men['mid']]['main'] = $men['menu'];

		$menuArr[$men['mid']]['child'][$n] = $men['higher'];  #提示这里不可解析

		//array_push($menuArr[$men['mid']]['child'], $men['higher']);

		$n++;

	}else{

		$n = 0;

		$menuArr[$men['mid']]['main'] = $men['menu'];

		$menuArr[$men['mid']]['child'] = $men['higher'];

	}

	$sign = $men['mid'];

}

print_r($menuArr);

#帮帮忙……

$list = array(

    0=>array('mid'=>1,'menu'=>'m1','level'=>1,'belong'=>0,'higher'=>'a1'),

    1=>array('mid'=>1,'menu'=>'m1','level'=>1,'belong'=>0,'higher'=>'a2'),

    2=>array('mid'=>1,'menu'=>'m1','level'=>1,'belong'=>0,'higher'=>'a3'),