php如何计算两个时间戳之间相差的日时分秒

/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(2015-03-20 16:20:30'),strtotime('2015-05-25 11:10:10')));