PHP: date now week

PHP获取上周、本周、上月、本月、本季度、上季度时间方法大全:

<?php
  echo '根据周获取时间:<br>';
  echo date("Ymd",strtotime("now")), "\n";
  echo date("Ymd",strtotime("-1 week Monday")), "\n";
  echo date("Ymd",strtotime("-1 week Sunday")), "\n";
  echo date("Ymd",strtotime("+0 week Monday")), "\n";
  echo date("Ymd",strtotime("+0 week Sunday")), "\n";

  echo '<br>'."*********第几个月:";
  echo date('n').'<br>';
  echo "*********本周周几:";
  echo date("w").'<br>';
  echo "*********本月天数:";
  echo date("t").'<br>';

  echo '上月起始时间:<br>';
  echo date("Y-m-d H:i:s",mktime(0, 0 , 0,date("m")-1,1,date("Y"))),"\n";
  echo date("Y-m-d H:i:s",mktime(23,59,59,date("m") ,0,date("Y"))),"\n";

  echo '<br>获取上月时间格式如下：2016-10<br>';
  echo date("Y-m",mktime(0, 0 , 0,date("m")-1,1,date("Y"))),"\n";

  echo '<br>本月起始时间:<br>';
  echo date("Y-m-d H:i:s",mktime(0, 0 , 0,date("m"),1,date("Y"))),"\n";
  echo date("Y-m-d H:i:s",mktime(23,59,59,date("m"),date("t"),date("Y"))),"\n";
   
  echo '<br>当月是第几季度:';
  echo $season = ceil((date('n'))/3);
  echo '<br>本季度起始时间:<br>';
  echo date('Y-m-d H:i:s', mktime(0, 0, 0,$season*3-3+1,1,date('Y'))),"\n";
  echo date('Y-m-d H:i:s', mktime(23,59,59,$season*3,date('t',mktime(0, 0 , 0,$season*3,1,date("Y"))),date('Y'))),"\n";
   
  echo '<br>上季度是第几季度:';
  echo $season = ceil((date('n'))/3)-1;
  echo '<br>上季度起始时间:<br>';
  echo date('Y-m-d H:i:s', mktime(0, 0, 0,$season*3-3+1,1,date('Y'))),"\n";
  echo date('Y-m-d H:i:s', mktime(23,59,59,$season*3,date('t',mktime(0, 0 , 0,$season*3,1,date("Y"))),date('Y'))),"\n";
  echo $data['order_date'] = date('Y-(m-1)',time());
?>
 输出结果：
    根据周获取时间:
    20161124 20161121 20161120 20161128 20161127 
    *********第几个月:11
    *********本周周几:4
    *********本月天数:30
    上月起始时间:
    2016-10-01 00:00:00 2016-10-31 23:59:59 
    获取上月时间格式如下：2016-10
    2016-10 
    本月起始时间:
    2016-11-01 00:00:00 2016-11-30 23:59:59 
    当月是第几季度:4
    本季度起始时间:
    2016-10-01 00:00:00 2016-12-31 23:59:59 
    上季度是第几季度:3
    上季度起始时间:
    2016-07-01 00:00:00 2016-09-30 23:59:59 2016-(11-1)s