How to calculate the difference between two timestamps in php

<?php 
//功能：计算两个时间戳之间相差的日时分秒
//$begin_time 开始时间戳
//$end_time 结束时间戳
function timediff($begin_time,$end_time)
{
	if($begin_time < $end_time){
		$starttime = $begin_time;
		$endtime = $end_time;
	}else{
		$starttime = $end_time;
		$endtime = $begin_time;
	}
	//计算天数
	$timediff = $endtime-$starttime;
	$days = intval($timediff/86400);
	//计算小时数
	$remain = $timediff%86400;
	$hours = intval($remain/3600);
	//计算分钟数
	$remain = $remain%3600;
	$mins = intval($remain/60);
	//计算秒数
	$secs = $remain%60;
	$res = array("day" => $days,"hour" => $hours,"min" => $mins,"sec" => $secs);
	return $res;
}
print_r(timediff(strtotime(&#39;2015-03-20 16:20:30&#39;),strtotime(&#39;2015-05-25 11:10:10&#39;)));
?>

Array ( [day] => 65 [hour] => 18 [min] => 49 [sec] => 40 )