PHP计算两个时间差的方法

<?php
//PHP计算两个时间差的方法
$startdate="2010-12-11 11:40:00";
$enddate="2012-12-12 11:45:09";
$date=floor((strtotime($enddate)-strtotime($startdate))/86400);
$hour=floor((strtotime($enddate)-strtotime($startdate))/86400/3600);
$minute=floor((strtotime($enddate)-strtotime($startdate))/86400/60);
$second=floor((strtotime($enddate)-strtotime($startdate))/86400/60);
echo $date."天<br>";
echo $hour."小时<br>";
echo $minute."分钟<br>";
echo $second."秒<br>";