date_default_timezone_set('PRC'); //设置中国时区

      echo "今天:", date("Y-m-d", time()), "<br>";

      echo "昨天:", date("Y-m-d", strtotime("-1 day")), "<br>";

      echo "明天:", date("Y-m-d", strtotime("+1 day")), "<br>";

      echo "一周后:", date("Y-m-d", strtotime("+1 week")), "<br>";

      echo "一周零两天四小时两秒后:", date("Y-m-d G:H:s", strtotime("+1 week 2 days 4 hours 2 seconds")), "<br>";

      echo "下个星期四:", date("Y-m-d", strtotime("next Thursday")), "<br>";

      echo "上个周一（大概率本周的周一）:" . date("Y-m-d", strtotime("last Monday")) . "<br>";

      echo "上周一:" . date("Y-m-d", strtotime("-1 week last Monday")) . "<br>";

      echo "一个月前:" . date("Y-m-d", strtotime("2018-03-31 last month")) . "<br>";//一个月前:2018-03-03

      echo "一个月后:" . date("Y-m-d", strtotime("2018-01-31 +1 month")) . "<br>";//一个月前:2018-03-03

      echo "十年后:" . date("Y-m-d", strtotime("+10 year")) . "<br>";

      echo '<hr>';

      //省略一些参数

      echo date('Y-m-d H:i:s'). '<br/>';

      echo strtotime(date('Y')),'----',date('Y-m-d H:i:s',strtotime(date('Y'))). '<br/>';//？？？？？？ 20:18:00 从哪来的

      echo strtotime(date('Y-m')),'----',date('Y-m-d H:i:s',strtotime(date('Y-m'))). '<br/>';//天 01，时分秒均为00

      echo strtotime(date('Y-m-d')),'----',date('Y-m-d H:i:s',strtotime(date('Y-m-d'))). '<br/>';//时分秒均为00

      echo strtotime(date('Y-m-d H')),'----',date('Y-m-d H:i:s',strtotime(date('Y-m-d H'))). '<br/>';//时间格式不识别

      echo strtotime(date('Y-m-d H:i')),'----',date('Y-m-d H:i:s',strtotime(date('Y-m-d H:i'))). '<br/>';//秒为00

      $date = '2018-2-17';

      echo '本月最后一天：' . date('Y-m-d', strtotime(date('Y-m-01', strtotime('+1 month'))) - 1) . '<br/>';

      echo '某月最后一天：' . date('Y-m-d', strtotime(date('Y-m-01', strtotime($date . ' +1 month'))) - 1) . '<br/>';

      //某月共多少天，可用于最后一天

      echo date('t', strtotime($date)) . '<br>';

      echo "一个月后:" . date("Y-m-d", strtotime("2018-01-01 +1 month")) . "<br>";

      echo "一个月后:" . date("Y-m-d", strtotime("2018-01-31 +1 month")) . "<br>";

      echo "一个月后:" . date("Y-m-d", strtotime("2018-02-01 +1 month")) . "<br>";

      echo "一个月后:" . date("Y-m-d", strtotime("2018-02-02 +1 month")) . "<br>";

      echo "一个月后:" . date("Y-m-d", strtotime("2018-02-28 +1 month")) . "<br>";

      echo "一个月后:" . date("Y-m-d", strtotime("2018-02-28 -1 month")) . "<br>";

      echo "一个月后:" . date("Y-m-d", strtotime("2018-02-29 -1 month")) . "<br>";

      $date = '2018-2-17';

      var_dump(getOneDayInWeek(7, $date));

   /**

   * @desc 获得某一日期所在周（周一到周日）中的某天

   * @param int $search 查找星期几，周一 1，周二 2。。。周六 6，周日7

   * @param null $date 基准日期

   * @return bool|string

   */

getOneDayInWeek($search, $date = NULL) {

    $date = !$date ? date('Y-m-d') : date('Y-m-d', strtotime($date));

    $search = intval($search);

    if ($search < 1 || $search > 7 || !$date) {

      return FALSE;

    }

    $weeks = ['', 'Mon', 'Tues', 'Wed', 'Thur', 'Fri', 'Sat', 'Sun'];

    $w = (int)date('w', strtotime($date));

    $w === 0 && $w = 7;

    $search > $w && $flag = ' next ';

    $search < $w && $flag = ' last ';

    return isset($flag) ? date("Y-m-d", strtotime($date . $flag . $weeks[$search])) : $date;

  }

      $deviationMonth = 1;

      $deviationDay = -1;

      $date = '2018-10-1';

      var_dump(getNextMonth($date, $deviationMonth, $deviationDay));

  /**

   * @desc 类似合同中下月减一天，试用期三个月后减一天

   *  正常 2018-01-17 --- 2018-02-16，2017-10-01---2017-10-31,2017-10-31 --- 2017-11-30

   *  2018-01-28 --- 2018-02-27,2018-01-29 --- 2018-02-28,2018-01-30 --- 2018-02-28,2018-01-31 --- 2018-02-28,2018-02-01 --- 2018-02-28，2018-02-02 --- 2018-03-01,2018-02-03 --- 2018-03-02

   * @param null $date 起始日期

   * @param int $deviationMonth 向后推几个月

   * @param int $deviationDay 向后推几天，一般是向前一天（-1）

   * @return bool|string

   */

getNextMonth($date = NULL, $deviationMonth = 1, $deviationDay = -1) {

    $timestamp = !$date ? time() : strtotime($date);

    $deviationMonth = intval($deviationMonth);

    $deviationDay = intval($deviationDay);

    if (!$deviationMonth || !$deviationDay || !$timestamp) {

      return FALSE;

    }

    $month = date('Y-m', strtotime(date('Y-m', $timestamp) . ' ' . $deviationMonth . ' month'));

    $day = date('d', $timestamp) + $deviationDay;

    $day > date('t', strtotime($month)) && $day = date('t', strtotime($month));

    return date('Y-m-d', strtotime($month . '-' . $day));

  }