PHP Logout on button click

Question

I made a login function using PHP, I have a variable called '$loggedIn' in a php class. How would I set this to false when a user clicks on the logout button?

Answer 1

1. Redirect to another page named logout.php where session_destroy(); or similar method is executed and set the value of $loggedIn to false there
2. Add an ajax call to send request to logout.php where session_destroy(); or similar method is executed and set the value of $loggedIn to false there

Upon destroying the session, redirect user to homepage/sign in page using header('location:signin.php');

Please note that the names logout.php or signin.php are just to make the example clear.

Answer 2

You should have a database with users to login, then you should check the DB to make sure the username and password is correct (and HASHED & SALTED). Then you should not use a $loggedIn variable, you need to use sessions.

The code below is highly abstracted and assumes a knowledge of database interaction. This page would run form something like signin.php

<?php

session_start();

auth()
{
    //DB logic here that compares $_POST['<username_field_name>'] and hashMethod($_POST['<password_field_name>']) to a returned row from the database
    //If it is valid return true
    if(<db logic conditions here>){
        return true;
    }
}

if(isset($_POST['<username_field_name>']) && isset($_POST['<password_field_name>'])))
{
    if(auth()){
        $_SESSION['loggedIn'] = 'true';
    }
}
else
{
    //Call for login form here
}

Once that is done you can simply destroy the session. http://php.net/manual/en/function.session-destroy.php

This code would be in logout.php.

<?php
session_destroy();
header('location:signin.php')

This is not by any means the best authentication at all! There are many factors that you need to worry about such as SQL injection but this gives you a core working system. What you really should do is learn a framework link Zend or Laravel that has built in best-practice authentication systems.

Laravel Secruity docs http://laravel.com/docs/security

Zend Framework Auth docs http://framework.zend.com/manual/1.12/en/learning.multiuser.authentication.html

I recommend Laravel if you are just learning.