<?php

/**

 * 求两个日期之间相差的天数

 * (针对1970年1月1日之后，求之前可以采用泰勒公式)

 * @param string $day1

 * @param string $day2

 * @return number

 */

function diffBetweenTwoDays ($day1, $day2)

{

  $second1 = strtotime($day1);

  $second2 = strtotime($day2);

  if ($second1 < $second2) {

    $tmp = $second2;

    $second2 = $second1;

    $second1 = $tmp;

  }

  return ($second1 - $second2) / 86400;

}

$day1 = "2013-07-27";

$day2 = "2013-08-04";

$diff = diffBetweenTwoDays($day1, $day2);

echo $diff."\n";

/**

 * 返回相差的月份数量

 * @param $date1 string 开始日期

 * @param $date2 string 结束日期

 * @return float|int

 */

function getMonthNum($date1,$date2){

    $date1_stamp=strtotime($date1);

    $date2_stamp=strtotime($date2);

    list($date_1['y'],$date_1['m'])=explode("-",date('Y-m',$date1_stamp));

    list($date_2['y'],$date_2['m'])=explode("-",date('Y-m',$date2_stamp));

    return abs($date_1['y']-$date_2['y'])*12 +$date_2['m']-$date_1['m'];

}