function getWeekday($time = '', $first = 1){
  if (!$time) $time = time();
  $sdefaultDate = date("Y-m-d", $time);
  //获取当前周的第几天 周日是 0 周一到周六是 1 - 6
  $w = date('w', strtotime($sdefaultDate));
  //获取本周开始日期，如果$w是0，则表示周日，减去 6 天
  $week_start = date('Ymd', strtotime("$sdefaultDate -" . ($w ? $w - $first : 6) . ' days'));
  //本周结束日期
  $week_end = date('Ymd', strtotime("$week_start +6 days"));
  return array("week_start" => $week_start, "week_end" => $week_end);
}