php 获取时间相差的月份和天数

function getMonthAndDay($date1,$date2){
    $datestart= date('Y-m-d',strtotime($date1));
    if(strtotime($datestart)>strtotime($date2)){
        $tmp=$date2;
        $date2=$datestart;
        $datestart=$tmp;
    }
    list($Y1,$m1,$d1)=explode('-',$datestart);
    list($Y2,$m2,$d2)=explode('-',$date2);
    $Y=$Y2-$Y1;
    $m=$m2-$m1;
    $d=$d2-$d1;
    if($d<0){
        $d+=(int)date('t',strtotime("-1 month $date2"));
        $m--;
    }
    if($m<0){
        $m+=12;
        $Y--;
    }

    $res['month'] = 0;
    if($Y == 0){
        $res['month'] = $m;
        $res['day']   = $d;
        return $res;
    }elseif($Y == 0 && $m == 0){
        $res['day']   = $d;
        return $res;
    }else{
        $res['month'] = $m+$Y*12;
        $res['day']   = $d;
        return $res;
    }
}