php 的时间处理函数

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    //获取两个日期区间所有日期，两个参数分别为两个日期 Y-m-d
    public function getDateFromRange($startdate, $enddate)
    {
        $stimestamp = strtotime($startdate);
        $etimestamp = strtotime($enddate);
        // 计算日期段内有多少天
        $days = ($etimestamp - $stimestamp) / 86400 + 1;
        // 保存每天日期
        $date = [];
        for ($i = 0; $i < $days; $i++) {
            $date[] = date('Y-m-d', $stimestamp + (86400 * $i));
        }
        return $date;
    }

调用：getDateFromRange('2017-1-8', '2017-2-8');

$date = date('oW', strtotime('2017-1-8'));   //获取日期所在哪年的第几周 $date = 201701
//获取 2017-1-8 这天属于 2017 的第 1 周。判断方式是从某一年的第一个 周一 开始计算新的一年的第一周
                                                                           
    //根据第几周获取当周的开始日期与最后日期
    function weekday($year,$weeknum){
        $firstdayofyear=mktime(0,0,0,1,1,$year);
        $firstweekday=date('N',$firstdayofyear);
        $firstweenum=date('W',$firstdayofyear);
        if($firstweenum==1){
            $day=(1-($firstweekday-1))+7*($weeknum-1);
            $startdate=date('Y-m-d',mktime(0,0,0,1,$day,$year));
            $enddate=date('Y-m-d',mktime(0,0,0,1,$day+6,$year));
        }else{
            $day=(9-$firstweekday)+7*($weeknum-1);
            $startdate=date('Y-m-d',mktime(0,0,0,1,$day,$year));
            $enddate=date('Y-m-d',mktime(0,0,0,1,$day+6,$year));
        }

        return array($startdate,$enddate);
    }

调用：weekday('2017', '01');

$month = date('Y-m', strtotime('2017-1-8')); //获取月份 $month = 2017-01

    //获取某个月的所有日期
    function getMonthDays($month = "this month", $format = "Y-m-d", $dateTimeZone = false) 
    {
        if(!$dateTimeZone) $dateTimeZone = new DateTimeZone("Asia/Shanghai");
        $start = new DateTime("first day of $month", $dateTimeZone);
        $end = new DateTime("last day of $month", $dateTimeZone);

        $days = array();
        for($time = $start; $time <= $end; $time = $time->modify("+1 day")) {
            $days[] = $time->format($format);
        }
        return $days;
    }

调用： getMonthDays('2017-01');

参照链接：
https://www.cnblogs.com/sanqiyi/p/8267019.html
https://www.cnblogs.com/leilei-1/p/8028183.html
https://segmentfault.com/q/1010000002415326