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$_SESSION variable is null before I set it to null

I have encountered a weird problem in my php code for a website I'm building:

php

I use the superglobal $_SESSION['recent'] for creating alerts on my webpages. For example if a user tries to sign in, but gives a wrong password, the sign-in form will send its data to a file login.php which checks if all the data is correct. If the data is correct, it will set $_SESSION['recent'] = 'login_succes' (and a few other things so the user is signed in), else it will set $_SESSION['recent'] = 'login_fail'. Next it will return to the homepage with header('location: http://www.example.com/').

$_SESSION['recent']

login.php

$_SESSION['recent'] = 'login_succes'

$_SESSION['recent'] = 'login_fail'

header('location: http://www.example.com/')

In this homepage, there is a chunk of php code with a switch statement which checks for all possible $_SESSION['recent'] values and will give an alert according to its value. This code looks a bit like this (I use bootstrap):

php

switch

$_SESSION['recent']

<?php switch ($_SESSION['recent']) { ?>
<?php case 'logout': ?>
<div class="container-fluid alert-fixed"><div class="alert alert-success alert-dismissible">
<button type="button" class="btn close" data-dismiss="alert">&times;</button>
You are signed out.
</div></div>
<?php break; case 'login_succes': ?>
<div class="container-fluid alert-fixed"><div class="alert alert-success alert-dismissible">
<button type="button" class="close" data-dismiss="alert">&times;</button>
You are signed in
</div></div>
<?php break; case 'login_fail': ?>
... (similar alert message)
<?php break; case 'not_loggedin': ?>
...
<?php break; case 'admin_change_succes': ?>
...
<?php break; case 'admin_change_fail': ?>
...
<?php break; } $_SESSION['recent'] = null; ?>


So what I expect it would do, is check for any notifications and show an alert message if necessary. When that is done, it would set $_SESSION['recent'] = null so this message wont keep showing showing on and on.

$_SESSION['recent'] = null

However, this is the problem: this works for the first 3 cases (logout, login_succes and login_fail), but for all the other cases, the alerts don't show, unless I delete the line $_SESSION['recent'] = null; (which I obviously don't want to delete, because then the alert messages will keep on showing on reloading).

logout

login_succes

login_fail

$_SESSION['recent'] = null;

Does anyone know what is causing this and how to tackle the problem? If you need more information, just ask for it.

Thanks!

session_start();

unset($_SESSION['recent'])

$_SESSION['recent']

$_SESSION['recent'] = null;

2 Answers
2

The code you posted in question looks like it should work as you expect. Most likely the problem is somewhere outside. To make sure that you have access to session value and clear it when script is done, you can do something like this

Add file FlashMessages.php with following content

FlashMessages.php

<?php
class FlashMessages {
private static $messages;
private static $sessionStarted = false;

public function __construct() {
if (!self::$sessionStarted) {
session_start();
self::$sessionStarted = true;
}
}

public function getMessage($name) {
if (!array_key_exists($name, self::$messages)) {
self::$messages[$name] = array_key_exists($name, $_SESSION) ? $_SESSION[$name] : null;
unset($_SESSION[$name]);
}

return self::$messages[$name];
}
}


In the place where you need to do your checking, add next code

<?php
require_once('FlashMessages.php');
$flashMessages = new FlashMessages();
switch ($flashMessages->getMessage('recent')) {
//...your code goes here
}


So I found my own solution (all of the above didn't work for me...):

in my code I would check for errors like this:

if (!$_SESSION['uid'] or !$_SESSION['login']) {
$_SESSION['recent'] = 'not_loggedin';
header('location: http://my.domain.com/');
}


however, there is al lot of other code following that chunk. I thought that the header statement would stop the following code from being executed, but this does not seem to be the case, changing that code to the following works for me:

header

if (!$_SESSION['uid'] or !$_SESSION['login']) {
$_SESSION['recent'] = 'not_loggedin';
header('location: http://my.domain.com/');
die();
}


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