上传到web时出现会话超时问题

我的代码在本地主机上工作得很好。然而，当我上传网页时，它显示会话结束时间为浏览器会话结束时，无论选择什么选项。下面是第一页

<pre><code>
session_start();
error_reporting(0);
if(isset($_SESSION['over18'])){
header("location: index.php");
}
if(isset($_SESSION['under18'])){
header("location: leave.php");
}
if(isset($_POST['submit'])){
$day = $_POST['day'];
$month = $_POST['month'];
$year = $_POST['year'];
$remember = $_POST['remember'];
$birthday = mktime(0,0,0,$month,$day, $year);
$difference = time()-$birthday;
$age = floor($difference/31556926);
if($age >= 18){
    $_SESSION['over18']=1;
    switch ($remember) {
        case 1:
            header("location: index.php?sessionid=1");
            break;
        case 2:
            header("location: index.php?sessionid=2");
            break;
        case 3:
            header("location: index.php?sessionid=3");
            break;
        case 4:
            header("location: index.php?sessionid=4");
            break;
        case 5:
            header("location: index.php?sessionid=5");
            break;
        case 6:
            header("location: index.php?sessionid=6");
            break;
        default:
            header("location: index.php?sessionid=1");
            break;
    }
} else {
    $_SESSION['under18']=0;
    header("location: leave.php");
}
}<!-- language: lang-none -->
p class="pos_fixed3">Remember me for: select name="remember">
option value="1">This Session Only</option>
    option value="2">1 Hour</option>
    option value="3">5 Hours</option>
    option value="4">1 Day</option>
    option value="5">1 Week</option>
    option value="6">1 Month</option> </p>
</select>
</pre></code>

我的代码index.php在下面

if(isset($_GET["sessionid"])){
$session = $_GET["sessionid"];
 } else {
$session = "";
}
switch ($session) {
        case '1':
            session_set_cookie_params();
            break;
        case '2':
            session_set_cookie_params('3600');
            break;
        case '3':
            session_set_cookie_params('18000');
            break;
        case '4':
            session_set_cookie_params('86400');
            break;
        case '5':
            session_set_cookie_params('604800');
            break;
        case '6':
            session_set_cookie_params('18144000');
            break;
        default:
            session_set_cookie_params('');
            break;
    }
session_start();
if(!$_SESSION['over18']){
header("location: age.php");
}