[函数]根据键值给二维数组排序（模仿sql语句排序）

function arrayOrderBy(array &$arr, $order = null) {
     if (is_null($order)) {
         return $arr;
     }
     $orders = explode(',', $order);
     usort($arr, function($a, $b) use($orders) {
         $result = array();
         foreach ($orders as $value) {
             list($field, $sort) = array_map('trim', explode(' ', trim($value)));
             if (!(isset($a[$field]) && isset($b[$field]))) {
                 continue;
             }
             if (strcasecmp($sort, 'desc') === 0) {
                 $tmp = $a;
                 $a = $b;
                 $b = $tmp;
             }
             if (is_numeric($a[$field]) && is_numeric($b[$field]) ) {
                 $result[] = $a[$field] - $b[$field];
             } else {
                 $result[] = strcmp($a[$field], $b[$field]);
             }
         }
         return implode('', $result);
     });
     return $arr;
 }