php编程---使用计算两个日期之间的天数

<?php/** * 求两个日期之间相差的天数 * (针对1970年1月1日之后) * @param string $day1 * @param string $day2 * @return int */function diffTwoDate(string $date1, string $date2) {    $timestamp1 = strtotime($date1);  $timestamp2 = strtotime($date2);      if($timestamp1 < $timestamp2) {    $tmp = $timestamp2;    $timestamp2 = $timestamp1;    $timestamp1 = $tmp;  }    $diff_days = ($timestamp1 - $timestamp2) / 86400;  return $diff_days;}$date1 = "2016-10-01";$date2 = "2016-11-04";$diff = diffTwoDate($date1,$date2);echo $diff;