function ddayTime($startday,$dday,$except_wdays){    
    $stime = strtotime($startday);
    
    $kwday = array('일','월','화','수','목','금','토');
    $wdays_code = array_keys(array_intersect($kwday,explode(',',$except_wdays)));

    $wdays_cnt = sizeof($wdays_code);
    $week_date_cnt = (7-$wdays_cnt);
    $week_cnt = floor($dday/$week_date_cnt);
    $week_left_date_cnt = $dday%$week_date_cnt;
    

    
    $last_wdays_dcnt=0;
    for($i=0;$i<=$week_left_date_cnt;$i++) {
        
        if(in_array((date('w',$stime)+$i)%7,$wdays_code)) {
            $last_wdays_dcnt++;
            $week_left_date_cnt++;
        }
    }
    
    $wdays_dcnt = ($week_cnt*$wdays_cnt);

    $tar_date = strtotime($startday.' + '.($dday+$wdays_dcnt+$last_wdays_dcnt).' days');
    return $tar_date;
}

$startdate = '2009-10-01';
$except_wdays = '월,수,금';
for($z=1;$z<=15;$z++) {
    echo $startdate.'일부터 ('.$except_wdays.')요일을 제외한 '.$z.'일후=>'.my_date(ddayTime($startdate,$z,$except_wdays))."<br>\r\n";
}

function my_date($timestemp) {
    $kwday = array('일','월','화','수','목','금','토');
    return date('Y-m-d (',$timestemp).$kwday[date('w',$timestemp)].")";
}


http://codepad.org/zR8xOy33