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
);