Logout user after a specific time of inactivity - php

Question

I am creating a website with more than 10 different php files. I want to check if the user is inactive, starting from the login page. So, if a user logs in and remains idle for a specific period of time, it has to log that user out. I am new to PHP and am currently using an answer to similar question which is
if (isset($_SESSION["LAST_ACTIVITY"])) {
if (time() - $_SESSION["LAST_ACTIVITY"] > 1800)) {
// last request was more than 30 minutes ago
session_unset(); // unset $_SESSION variable for the run-time
session_destroy(); // destroy session data in storage
} else if (time() - $_SESSION["LAST_ACTIVITY"] > 60) {
$_SESSION["LAST_ACTIVITY"] = time(); // update last activity time stamp
}
}
I found the answer here:
expire session when there is no activity in PHP
I have created a separate page called session.php and pasted the code in the above link. Then I included the file session.php in my login page (which checks for the credentials entered and logs a user in). The problem is, the if loop is not being run and I do not know how to define $_SESSION['LAST_ACTIVITY'] variable. I used the following in my login page:
$query = "SELECT *
FROM user_details
WHERE username = '$username'
AND password = '$password'";
$result = mysqli_query($dbconnect, $query);
$row = mysqli_fetch_array($result);
$count = mysqli_num_rows($result);
if ($count == 1) {
session_start();
echo "Welcome " .$username. "</br>";
$_SESSION['username'] = $username;
$login_time = time();
$_SESSION["LAST_ACTIVITY"] = $login_time ;
include('session.php');
I also tried including session.php at the beginning of the file but of no use. The problem is: time() - $_SESSION["LAST_ACTIVITY"] is being equalled to 0. How do I store last activity time and compare it with the current time? Also, should I include session.php in every other webpage file for the website to check user activity ? If yes, should I include it at the beginning or at the end ?

Answer 1

This code will solved your problem for session timeout.
<?php
// set timeout period in seconds
$inactive = 60; //after 60 seconds the user gets logged out
// check to see if $_SESSION['timeout'] is set
if(isset($_SESSION['timeout']) ) {
$session_life = time() - $_SESSION['timeout'];
if($session_life > $inactive)
{
session_destroy();
header("Location: Logout.php");
}
}
$_SESSION['timeout'] = time();
?>