对于会话变量的未定义索引，即使我已经设置了cookie

Question

I am trying to set cookies to a php session variable so that a session does not expire for 2 months. The problem I am getting though is that after about 3 hours, when I refresh the page, I get a undefined index for $_SESSION['id'] in line 30. But I don't get the undefined index for $_SESSION['id'] in between lines 20-23.

Why am I still getting undefined indexes even though I have set cookies for this session variable?

$inTwoMonths = 60 * 60 * 24 * 60 + time();
    setcookie('id', 'ID', $inTwoMonths);


    //line 20-23
    if (isset($_POST['id'])) {

    $_SESSION['id'] = $_POST['id'];

    }

    //line 30
    <?php echo $_SESSION['id'] ?>

Answer 1

SESSION != COOKIE.

You must set SESSION TTL in php.ini (20min default).

On line 20-23 you dont get undefined index, coz you setting var. But on line 30 you trying to read undefined variable(coz you dont set-up it before.)

Try something like this:

$_SESSION['id'] = $_COOKIE['id'];

Also you need use session_start(); to init session.