当$user_list为0时，竟然会再次重新调用，$user_list再次为0时，才会返回$result

function count_user_order($user_list_str, $limit = 4, $times = 1)
{
  static $result = array('users_count'=>array(), 'order_number'=>array(), 'order_amount'=>array());
  $sql = 'SELECT user_id FROM '.$GLOBALS['ecs']->table('users')." WHERE parent_id IN (%s)"; // 统计顾客
  $user_list = $GLOBALS['db']->getCol(sprintf($sql, $user_list_str));

  $sql_order = 'SELECT SUM(order_amount) order_amount,COUNT(*) order_number FROM '
  .$GLOBALS['ecs']->table('order_info')." WHERE pay_status=2 AND user_id IN (%s)"; // 统计订单数量及金额
  list($result['order_amount'][], $result['order_number'][]) = $GLOBALS['db']->getRow(sprintf($sql_order, $user_list_str));

  $result['users_count'][] = count($user_list);
  if ((!$limit || $times < $limit) && count($user_list)) {
    $user_list_str = implode(',', $user_list);
    count_user_order($user_list_str, $limit, ++$times);
  }

  return $result;
}

或许图片更容易看些：