Comment trier un tableau à deux dimensions en PHP

function multi_compare($a, $b)
{
  $val_arr = array(
      'gold'=>'asc',
      'silver'=>'desc'//还可以增加额外的排序条件
  );
  foreach($val_arr as $key => $val){
    if($a[$key] == $b[$key]){
      continue;
    }
    return (($val == &#39;desc&#39;)?-1:1) * (($a[$key] < $b[$key]) ? -1 : 1);
  }
  return 0;
}
$arr = array(
  array(&#39;gold&#39;=>1, &#39;silver&#39;=>2),
  array(&#39;gold&#39;=>8, &#39;silver&#39;=>10),
  array(&#39;gold&#39;=>8, &#39;silver&#39;=>8),
  array(&#39;gold&#39;=>2, &#39;silver&#39;=>1),
);
uasort($arr, &#39;multi_compare&#39;);
print_r($arr);

Array
(
  [0] => Array
    (
      [gold] => 1
      [silver] => 2
    )
  [3] => Array
    (
      [gold] => 2
      [silver] => 1
    )
  [1] => Array
    (
      [gold] => 8
      [silver] => 10
    )
  [2] => Array
    (
      [gold] => 8
      [silver] => 8
    )
)