Change SESSION variable value

Question

I've been attempting to figure this out for a little while now, and it's driving me nuts. Basically I have a form for US and Canadian users. There's a link at the bottom of the form for Canadian users, which directs users to can-sesssion.php, which contains:

<?php
if (isset($_SESSION['can'])) {
    session_start();
    session_destroy();
    session_unset();
    session_start();
    $_SESSION['can'] = 2;
}
else {
    session_start();
    $_SESSION['can'] = 1;
}
header('Location: '. $_SERVER['HTTP_REFERER'] . '');
?>

Basically, if they click on the link, it sets $_SESSION['can'] = 1. Now There's another option, and if they click that link, it takes them back to this page, and the session should be destroyed and a new value is set (well, that's what it's supposed to do). Problem is, I've printed out $_SESSION['can'], and it's still retaining that old value after going to that page. Is there a better way to do this, or is there something wrong w/ my code? Thanks for the help.

Answer 1

This is what you wrote:

if (isset($_SESSION['can'])) {
    session_start();

session_start is the function which reads the session file associated with the user's PHPSESSID cookie and populates $_SESSION, so you're trying to read from the array before it has any values.

You need to call session_start before you check if $_SESSION['can'] has a value.

You also do not need to destroy and create a new session just to change a value.

<?php
session_start();
if (isset($_SESSION['can'])) {
    $_SESSION['can'] = 2;
} else {
    $_SESSION['can'] = 1;
}
header('Location: '. $_SERVER['HTTP_REFERER'] . '');
?>

Answer 2

Try this: (using only one session_start())

<?php
session_start();
if (isset($_SESSION['can'])) {
    $_SESSION['can'] = 2;
}
else {
    $_SESSION['can'] = 1;
}
header('Location: '. $_SERVER['HTTP_REFERER'] . '');
?>