// 獲取指定日期內月份的起始日期
protected function to_month($begin_at , $end_at) {
	$month1 = explode("-", $begin_at);
        $month2 = explode("-", $end_at);
        $count = abs($month1[0] - $month2[0]) * 12 + abs($month1[1] - $month1[1]);
        $arr = array();
        for ($i = 0; $i <= $count - 1; ++$i) {
            $t
 
 = strtotime("-$i month");
            $arr[] = explode('/', date('Y-m-01', $t) . '/' . date('Y-m-', $t) . date('t', $t));
        }
        return $arr;
}

// 根據第幾周獲取該周的起始日期
    protected function week_day($year, $week = 1) {
        $year_start = mktime(0, 0, 0, 1, 1, $year);
        $year_end = mktime(0, 0
 
, 0, 12, 31, $year);

        // 判斷第一天是否為第一週的開始
        if (intval(date('W', $year_start)) === 1) {
            $start = $year_start;//把第一天做為第一週的開始
        } else {
            $week++;
            $start = strtotime('+1 monday', $year_start);//把第一個週一作為開始
        }

        // 第幾周的開始時間
        if ($week === 1
 
) {
            $weekday['start'] = $start;
        } else {
            $weekday['start'] = strtotime('+' . ($week - 0) . ' monday', $start);
        }

        // 第幾周的結束時間
        $weekday['end'] = strtotime('+1 sunday', $weekday['start']);
        if (date('Y', $weekday['end']) != $year) {
            $weekday['end'] = $year_end;
        }
        return [
            'begin_at' => date("Y-m-d", $weekday['start']),
            'end_at' => date("Y-m-d", $weekday['end'])
        ];
    }