switch ($exchange_time) {
 
   
  case 1 : // 本月
 
   
  // 本月起始时间:
 
   
  $begin_time = date ( "Y-m-d H:i:s", mktime ( 0, 0, 0, date ( "m" ), 1, date ( "Y" ) ) );
 
   
  $end_time = date ( "Y-m-d H:i:s", mktime ( 23, 59, 59, date ( "m" ), date ( "t" ), date ( "Y" ) ) );
 
   
  break;
 
   
  case 2 : // 上个月
 
   
  // 上个月的起始时间:
 
   
  $begin_time = date('Y-m-01 00:00:00',strtotime('-1 month'));
 
$end_time = date("Y-m-d 23:59:59", strtotime(-date('d').'day'));
 
   
  break;
 
   
  case 3 : // 上上个月
 
   
  $begin_time =  date("Y-m-d H:i:s",mktime(0, 0 , 0,date("m")-2,1,date("Y")));
 
   
  $end_time =  date("Y-m-d H:i:s",mktime(23,59,59,date("m")-1 ,0,date("Y")));
 
   
  break;
 
   
  }
  
 
 
 
 
 ​
​

 

      echodate("Ymd",strtotime("now")),"\n";
 
     echodate("Ymd",strtotime("-1 week Monday")),"\n";
 
     echodate("Ymd",strtotime("-1 week Sunday")),"\n";
 
     echodate("Ymd",strtotime("+0 week Monday")),"\n";
 
     echodate("Ymd",strtotime("+0 week Sunday")),"\n";
 
  
 
     echo"*********第几个月:";
 
     echodate('n');
 
     echo"*********本周周几:";
 
     echodate("w");
 
     echo"*********本月天数:";
 
     echodate("t");
 
     echo"*********";
 
  
 
     echo'<br>上周起始时间:<br>';
 
     echodate("Y-m-d H:i:s",mktime(0, 0 , 0,date("m"),date("d")-date("w")+1-7,date("Y"))),"\n";
 
     echodate("Y-m-d H:i:s",mktime(23,59,59,date("m"),date("d")-date("w")+7-7,date("Y"))),"\n";
 
     echo'<br>本周起始时间:<br>';
 
     echodate("Y-m-d H:i:s",mktime(0, 0 , 0,date("m"),date("d")-date("w")+1,date("Y"))),"\n";
 
     echodate("Y-m-d H:i:s",mktime(23,59,59,date("m"),date("d")-date("w")+7,date("Y"))),"\n";
 
  
 
     echo'<br>上月起始时间:<br>';
 
     echodate("Y-m-d H:i:s",mktime(0, 0 , 0,date("m")-1,1,date("Y"))),"\n";
 
     echodate("Y-m-d H:i:s",mktime(23,59,59,date("m") ,0,date("Y"))),"\n";
 
     echo'<br>本月起始时间:<br>';
 
     echodate("Y-m-d H:i:s",mktime(0, 0 , 0,date("m"),1,date("Y"))),"\n";
 
     echodate("Y-m-d H:i:s",mktime(23,59,59,date("m"),date("t"),date("Y"))),"\n";
 
  
 
     $season= ceil((date('n'))/3);//当月是第几季度
 
     echo'<br>本季度起始时间:<br>';
 
     echodate('Y-m-d H:i:s',mktime(0, 0, 0,$season*3-3+1,1,date('Y'))),"\n";
 
     echodate('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";
 
  
 
     $season= ceil((date('n'))/3)-1;//上季度是第几季度
 
     echo'<br>上季度起始时间:<br>';
 
     echodate('Y-m-d H:i:s',mktime(0, 0, 0,$season*3-3+1,1,date('Y'))),"\n";
 
     echodate('Y-m-d H:i:s',mktime(23,59,59,$season*3,date('t',mktime(0, 0 , 0,$seas））