用strtotime()和date()函数算出2019年9月的周日日期

strtotime---用于接收两个参数，第一个参数是格式化的日期数据如：date('Y-m-d'),第二个参数有如'+7 day'

• 函数版

<?php
$firstsunday = strtotime(date('Y-m-01'));
$thisy = intval(date('m'));
$diffdays=0;
$count = 0;
if (date('w',strtotime(date('Y-m-01')))!=0)
{$diffdays=7-date('w',strtotime(date('Y-m-01')));
}
else{$count++;
}
$startdate =strtotime(date('Y-m-01')."+".$diffdays."day");
while (True)
{if ($thisy!=intval(date('m',$startdate))){break;}echo date('Y-m-d',$startdate)."\n";$startdate = strtotime(date('Y-m-d',strtotime(date('Y-m-d',$startdate)."+7 day")));//
}

结果

2019-09-01
2019-09-08
2019-09-15
2019-09-22
2019-09-29

•  类版本---date()的参数可以是‘2019-09-20’这样的字符串,如同date('2019-09-20')或者是strtotime返回的整型数如同date('Y-m-d',strtotime('2019-09-20))

class mycalendar
{function __construct($year,$mon){$this->nianyue=$year.'-'.$mon.'-'.'01';$this->firstday=strtotime(date($this->nianyue));$this->m = intval(date('m',$this->firstday));$this->wdaylist=array();echo "时间戳:".date('Y-m-d',$this->firstday)."\n";}function startday(){$w = date('w',$this->firstday);$diffdays=0;if ($w!=0){$diffdays= 7-$w;}$this->firstday = strtotime(date('Y-m-d',strtotime($this->nianyue))."+".$diffdays." day");//array_push($this->wdaylist,$w);//echo "\n".date('Y-m-d',$this->firstday);//echo "\n".$this->firstday;return $this->firstday;}function addwday(){$curday = $this->startday();while (true){if(intval(date('m',$curday)!=$this->m)){break;}echo date('Y-m-d',$curday)."\n";array_push($this->wdaylist,date('Y-m-d',$curday));$curday=strtotime(date('Y-m-d',$curday)."+7 day");}return $this->wdaylist;}
}
$mycal = new mycalendar(2019,10);
var_dump($mycal->addwday());

 

结果：

时间戳:2019-10-01
2019-10-06
2019-10-13
2019-10-20
2019-10-27
array(4) {
  [0]=>
  string(10) "2019-10-06"
  [1]=>
  string(10) "2019-10-13"
  [2]=>
  string(10) "2019-10-20"
  [3]=>
  string(10) "2019-10-27"
}

•  计算月末最后一天

echo date('Y-m-d',strtotime(date('2019-10-01')."+1 month -1 day"));

输出结果：

2019-10-31

•  注意！对于日期计算一定要，正确的使用参数，否则将会出错

$lastday = strtotime(date('Y-m-d',$this->time)."+1 day");#正确

$lastday = strtotime(date($this->time)."+1 day");#错误，这样会返回1970-01-01