Creating a Simple Login/Logout System in PHP for Beginners

Setting up a login and logout system in PHP is straightforward, making it an ideal project for beginners. This guide will walk you through the steps to create a basic authentication system. We will create four files and a MySQL table to handle the user login and logout functionality.

Files Overview

login.php
authenticate.php
index.php
logout.php

MySQL Table Creation

First, we need to create a MySQL table to store user data. Use the following SQL script to create a users table:

CREATE TABLE IF NOT EXISTS `users` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `username` varchar(50) NOT NULL,
  `password` varchar(150) NOT NULL,
  `name` varchar(50) NOT NULL,
  `active` int(11) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM;

Step 1: Creating the Login Form (`login.php`)

We start by creating a login form where users can input their username and password.

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Login</title>
</head>
<body>
    <form action="authenticate.php" method="post">
        <table width="100%" cellpadding="4" cellspacing="0" border="0">
            <tr>
                <td>Username:</td>
                <td><input type="text" name="username" required></td>
            </tr>
            <tr>
                <td>Password:</td>
                <td><input type="password" name="password" required></td>
            </tr>
            <tr>
                <td></td>
                <td><input type="submit" value="Login"></td>
            </tr>
        </table>
    </form>
</body>
</html>

Explanation

Form Action: The form’s action is set to authenticate.php, which means the data will be submitted to authenticate.php for processing.
Input Fields: Two fields are created for username and password. Both fields are required for submission.
Submit Button: A submit button is provided to send the form data.

Step 2: Authenticating the User (`authenticate.php`)

This file will handle the authentication logic.

<?php
session_start();
$conn = new mysqli('localhost', 'root', 'pass', 'test');

if ($conn->connect_error) {
    die('Connection failed: ' . $conn->connect_error);
}

if ($_SERVER['REQUEST_METHOD'] == 'POST') {
    $username = trim($_POST['username']);
    $password = trim($_POST['password']);

    if ($username != '') {
        $stmt = $conn->prepare("SELECT * FROM users WHERE username = ? AND active = 1");
        $stmt->bind_param('s', $username);
        $stmt->execute();
        $result = $stmt->get_result();
        $user = $result->fetch_assoc();

        if ($user && password_verify($password, $user['password'])) {
            $_SESSION['user_id'] = $user['id'];
            $_SESSION['username'] = $user['username'];
            header('Location: index.php');
            exit;
        } else {
            header('Location: login.php?err=1');
            exit;
        }
    }
}
?>

Explanation

Session Start: We start a session to store user data upon successful login.
Database Connection: A connection to the MySQL database is established.
POST Check: We check if the form was submitted via POST.
User Validation: We retrieve the user record from the database and verify the password using password_verify().
Session Variables: If the user is authenticated, their ID and username are stored in session variables.
Redirection: Upon successful authentication, the user is redirected to index.php. If authentication fails, the user is redirected back to the login page with an error.

Step 3: Creating the Index Page (`index.php`)

This page is accessible only to logged-in users.

<?php
session_start();
if (!isset($_SESSION['user_id'])) {
    header('Location: login.php');
    exit;
}
?>
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Home</title>
</head>
<body>
    <p>You are now logged in</p>
    <a href="logout.php">Logout</a>
</body>
</html>

Explanation

Session Check: We check if the user ID is set in the session. If not, the user is redirected to the login page.
Logged In Message: A simple message is displayed indicating that the user is logged in.
Logout Link: A link is provided to log out.

Step 4: Creating the Logout Script (`logout.php`)

This script handles the user logout process.

<?php
session_start();
session_unset();
session_destroy();
header('Location: login.php');
exit;
?>

Explanation

Session Handling: The session is started, and then all session variables are unset, and the session is destroyed.
Redirection: The user is redirected to the login page after logging out.

Conclusion

With these steps, you have created a basic login/logout system in PHP. This system includes:

A login form for user input.
An authentication script to verify user credentials.
A protected page accessible only to authenticated users.
A logout script to end the user session.

Files Overview

MySQL Table Creation

Step 1: Creating the Login Form (login.php)

Explanation

Step 2: Authenticating the User (authenticate.php)

Explanation

Step 3: Creating the Index Page (index.php)

Explanation

Step 4: Creating the Logout Script (logout.php)

Explanation

Conclusion

Step 1: Creating the Login Form (`login.php`)

Step 2: Authenticating the User (`authenticate.php`)

Step 3: Creating the Index Page (`index.php`)

Step 4: Creating the Logout Script (`logout.php`)