PHP时间处理

$start = "2013-9-26";
$end = "2013-9-27";
$start = strtotime($startdate);//开始时间 时间戳
$end = strtotime($enddate);//结束时间 时间戳
$diff = ($end-$start)>0?$end - $start:$start-$end; //得出时间戳差值
$d = ceil($diff/3600/24);
print_r($d);
//输出5

$startdate ="2013-9-26";  //开始时间
$start = strtotime($startdate); //转成时间戳
$getstartdate =  getdate($start); //获得日期
$n =5; //n天后
$enddate = date('Y-m-d',mktime(0,0,0,$getstartdate['mon'],$getstartdate['mday']+$n,$getstartdate['year']));  //获取n天后的日期
print_r($enddate); //输出2013-10-01