一个数组排序的问题

array(22) {
  [0]=>
  array(6) {
    ["CheckID"]=>
    string(16) "1001"
    ["PicMemo"]=>
    string(3) "102"
  }
  [1]=>
  array(6) {
    ["CheckID"]=>
    string(16) "1005"
    ["PicMemo"]=>
    string(3) "15"
  }
  [2]=>
  array(6) {
    ["CheckID"]=>
    string(16) "1002"
    ["PicMemo"]=>
    string(3) "102"
  }
  [3]=>
  array(6) {
    ["CheckID"]=>
    string(16) "1003"
    ["PicMemo"]=>
    string(3) "171"
  }
  [4]=>
  array(6) {
    ["CheckID"]=>
    string(16) "1004"
    ["PicMemo"]=>
    string(3) "102"
  }
  [5]=>
  array(6) {
    ["CheckID"]=>
    string(16) "1005"
    ["PicMemo"]=>
    string(3) "171"
  }
  ...
 }

数组$arr;按照 'PicMemo'排序 将相同的值放在一起，键重组；
3q了！
[解决办法]
foreach($ar as $v) $r[] = $v['PicMemo'];
array_multisort($r, $ar);
print_r($ar);