PHP Session Variable Randomly Unsets

Question

I have a PHP Session that I am using to manage my administration panel of my website. This uses two variables to monitor the session, lastAction and user. Recently, on one particular page of my website, the session variable user will randomly unset entirely and send the user back to the login page, but I cannot seem to figure out why.

session_start();

$fn = "timeout.txt";
$fh = fopen($fn,'r');
$to = fread($fh,filesize($fn));

if(abs(time()-$_SESSION["lastAction"]) > $to)
{
    session_unset();
    die("Timeout");
}

var_dump($_SESSION);

//Set timeout back to 0
$_SESSION["lastAction"] = time();

if($_SESSION["user"] != "...")
{
    die("Invalid User");
    header("Location:/login");
}

I never get the Timeout error, only the Invalid User error.

Sometimes when I dump the session variable, I get the array of two values, lastAction and user, but then, simply by reloading the page only a few seconds later, user gets unset, but lastAction does not.

Also, in this instance, I am reloading the page through javascript: parent.location='';

Any ideas on what might be causing this?

Is it possible that the sesssion has exceeded the php session timeout setting? — Barbara Laird
– Barbara Laird, Commented Oct 18, 2013 at 20:11
I don't think so; this happens randomly, and if I go directly to this page after logging in (perhaps only a minute later), 1 in 5 refreshes will unset the variable. — Liftoff
– Liftoff, Commented Oct 18, 2013 at 20:13

Gary Hayes · Accepted Answer · 2013-10-18 20:14:57Z

3

This most likely has to do with your Header. The session variables are only good within the domain they are set in. For example, if you set the session vars in www.example.com, but then your header redirects to example.com, you will not have your session vars to use, same as if you redirected to mobile.example.com. Change that relative path I see in your code and see if that is what is causing it.

answered Oct 18, 2013 at 20:14

Gary Hayes

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4 Comments

Liftoff Over a year ago

What relative path do you mean in particular, because I'm still getting logged out sometimes.

Gary Hayes Over a year ago

I don't know, I can't see all the pages or all the code that could be causing it. That is for you to look through. It could be a javascript redirect too, not just a header redirect. The main thing is to be consistent with your domains.

Liftoff Over a year ago

Is it possible that a 404 error on an image could be causing this?

Liftoff Over a year ago

Yep that was it! A 404 error was causing it. Thanks for your help!

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