php array_multisort 排序

$arr = Array
(
4875965=>array(
     'followCount'=> 8,
'friendOffriend'=> 4875965,
'friend' => array(49845,56565,67657)
),
  54353=> array(
     'followCount'=> 3,
'friendOffriend'=> 54353,
'friend' => array(49845,56565,67657)
),
  86575=> array(
     'followCount'=> 12,
'friendOffriend'=> 86575,
'friend' => array(49845,56565,67657)
),
  3434=> array(
     'followCount'=> 5,
'friendOffriend'=> 3434,
'friend' => array(49845,56565,67657)
),
);


$arr2 = Array
(
4875965=>8,
54353=> 3,
86575=>12,
3434=>5
);