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.

You should be aware that the HTTP_REFERER is not a header you can rely on being set, or being set to the actual referring page. It is optional and the browser can send whatever it wants. — Dan Grossman
– Dan Grossman, Commented Aug 9, 2011 at 15:57
Is there an option that would be more useful, or would it be more pragmatic to simply include this php within the page? — William Orazi
– William Orazi, Commented Aug 9, 2011 at 16:04
You put the code wherever you want to change the session variable. You can change things as many times as you need without sending anyone to a new page. — Dan Grossman
– Dan Grossman, Commented Aug 9, 2011 at 16:26

Dan Grossman · Accepted Answer · 2011-08-09 15:52:44Z

11

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'] . '');
?>

answered Aug 9, 2011 at 15:52

Dan Grossman

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4 Comments

William Orazi Over a year ago

Gotcha. Yea, I was just destroying the session as another last ditch effort, but obviously it wouldn't have worked since I didn't initialize the session in the first place.

William Orazi Over a year ago

I'm showing the other response came up first on my end. I appreciate your quick response though.

William Orazi Over a year ago

Here's what shows on my end: answered 25 mins ago - Neal ----- answered 27 mins ago - Dan

William Orazi Over a year ago

Wow, sorry bud, my mind wasn't there for a minute. Fixed it.

Naftali · Accepted Answer · 2011-08-09 15:54:40Z

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'] . '');
?>

answered Aug 9, 2011 at 15:54

Naftali

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2 Comments

William Orazi Over a year ago

Perfecto! Any idea why the multiple session_start()'s were breaking it?

Naftali Over a year ago

they weren't, you were just calling it at the wrong time ^_^

Just Another Coder · Accepted Answer · 2019-09-01 13:03:06Z

0

You may want to include

if (session_status() == PHP_SESSION_NONE) {
  session_start();
}

instead of just plain

session_start();

answered Sep 1, 2019 at 13:03

Just Another Coder

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