$date = array_column($info['rows'], 'gw');//多维数组按照纵向(列)取出
array_multisort($date,SORT_ASC,$info['rows']);//例子:合并两个数组,并按数字降序排列:
$a1=array(1,30,15,7,25);
$a2=array(4,30,20,41,66);
$num=array_merge($a1,$a2);
array_multisort($num,SORT_DESC,SORT_NUMERIC);
print_r($num);