Session value in PHP not expiring - php

Question

I have set two session variables set as:
$_SESSION['logged_in'] = 1;
$_SESSION['last_acted_on'] = time();
I am trying to reset the value of the session variable logged_in with:
<?php
session_start();
if( isset($_SESSION['last_acted_on']) && (time() - $_SESSION['last_acted_on'] > 120) ){ //2mins
session_unset('last_acted_on'); // unset $_SESSION variable for the run-time
session_unset('logged_in');
session_unset();
unset($_SESSION['last_acted_on']);
unset($_SESSION['logged_in']);
session_destroy(); // destroy session data in storage
return;
}
else{
$_SESSION['last_acted_on'] = time();
}
?>
But there is no effect and logged_in stays as 1. Any advice?
EDIT: I have updated my code as:
if( isset($_SESSION['last_acted_on']) && (time() - strtotime($_SESSION['last_acted_on']) > 120) ){ //2mins
unset($_SESSION['last_acted_on']); // unset $_SESSION variable for the run-time
unset($_SESSION['logged_in']);
session_unset();
session_destroy(); // destroy session data in storage
return;
}
$_SESSION['last_acted_on'] = time();
Also, when I refresh the page or navigate back and forth on the page, the session value is unset. Why is it not unset after the time period of 2mins? Please note that the page refresh that is expiring the session variable is calling unsetsession.php file.

Answer 1

Wronng usage of session_unset.
void session_unset ( void )
What you need is
unset($_SESSION['yourvalue'])

Answer 2

I believe there is issue with session variable unsetting. If you intend to flush the session itself, you can use session_destroy(), which will clear the $_SESSION array. Otherwise, you can use the unset() function, as stated here.
Note: If $_SESSION (or $HTTP_SESSION_VARS for PHP 4.0.6 or less) is
used, use unset() to unregister a session variable, i.e. unset
($_SESSION['varname']);.
Or more easily, you can simply set their values to null or 0 and you can put a check on their empty condition, as below:
<?php
session_start();
$session = &$_SESSION;
if( !empty($session['last_acted_on']) && (time() - $session['last_acted_on'] > 120) ){ //2mins
unset($session['last_acted_on']); // unset $_SESSION variable for the run-time
unset($session['logged_in']);
return;
}
else{
$session['last_acted_on'] = time();
}