From what I understood it may be,
session_start(); !isset($_SESSION['loggedin'])) and maybe few other lines

After the user registers successfully, I want him to be redirected to home.php
Could you please show me an exact snippet?

register.php

<?php
include 'main.php';
// Now we check if the data was submitted, isset() function will check if the data exists.
if (!isset($_POST['username'], $_POST['password'], $_POST['cpassword'], $_POST['email'])) {
    // Could not get the data that should have been sent.
    exit('<div >Please complete the registration form!</div>');
}
// Make sure the submitted registration values are not empty.
if (empty($_POST['username']) || empty($_POST['password']) || empty($_POST['email'])) {
    // One or more values are empty.
    exit('<div >Please complete the registration form!</div>');
}
// Check to see if the email is valid.
if (!filter_var($_POST['email'], FILTER_VALIDATE_EMAIL)) {
    exit('<div >Email is not valid!</div>');
}
// Username must contain only characters and numbers.
if (!preg_match('/^[a-zA-Z0-9] $/', $_POST['username'])) {
    exit('<div >Username is not valid!</div>');
}
// Password must be between 5 and 20 characters long.
if (strlen($_POST['password']) > 20 || strlen($_POST['password']) < 5) {
    exit('<div >Password must be between 5 and 20 characters long!</div>');
}
// Check if both the password and confirm password fields match
if ($_POST['cpassword'] != $_POST['password']) {
    exit('<div >Passwords do not match!</div>');
}
// Check if the account with that username already exists
$stmt = $pdo->prepare('SELECT id, password FROM accounts WHERE username = ? OR email = ?');
$stmt->execute([ $_POST['username'], $_POST['email'] ]);
$account = $stmt->fetch(PDO::FETCH_ASSOC);
// Store the result so we can check if the account exists in the database.
if ($account) {
    // Username already exists
    echo '<div >Username and/or email exists!</div>';
} else {
    // Username doesn't exist, insert new account
    $stmt = $pdo->prepare('INSERT INTO accounts (username, password, email, activation_code) VALUES (?, ?, ?, ?)');
    // We do not want to expose passwords in our database, so hash the password and use password_verify when a user logs in.
    $password = password_hash($_POST['password'], PASSWORD_DEFAULT);
    $uniqid = account_activation ? uniqid() : 'activated';
    $stmt->execute([ $_POST['username'], $password, $_POST['email'], $uniqid ]);
    if (account_activation) {
        // Account activation required, send the user the activation email with the "send_activation_email" function from the "main.php" file
        send_activation_email($_POST['email'], $uniqid);
        echo 'Please check your email to activate your account!';
    } else {
        echo '<div >You have successfully registered, you can now login!</div>';

    }
}
?>

main.php

<?php
// The main file contains the database connection, session initializing, and functions, other PHP files will depend on this file.
// Include thee configuration file
include_once 'config.php';
// We need to use sessions, so you should always start sessions using the below code.
session_start();
// No need to edit below
try {
    $pdo = new PDO('mysql:host=' . db_host . ';dbname=' . db_name . ';charset=' . db_charset, db_user, db_pass);
} catch (PDOException $exception) {
    // If there is an error with the connection, stop the script and display the error.
    exit('Failed to connect to database!');
}
// The below function will check if the user is logged-in and also check the remember me cookie
function check_loggedin($pdo, $redirect_file = 'index.php') {
    // Check for remember me cookie variable and loggedin session variable
    if (isset($_COOKIE['rememberme']) && !empty($_COOKIE['rememberme']) && !isset($_SESSION['loggedin'])) {
        // If the remember me cookie matches one in the database then we can update the session variables.
        $stmt = $pdo->prepare('SELECT * FROM accounts WHERE rememberme = ?');
        $stmt->execute([ $_COOKIE['rememberme'] ]);
        $account = $stmt->fetch(PDO::FETCH_ASSOC);
        if ($account) {
            // Found a match, update the session variables and keep the user logged-in
            session_regenerate_id();
            $_SESSION['loggedin'] = TRUE;
            $_SESSION['name'] = $account['username'];
            $_SESSION['id'] = $account['id'];
            $_SESSION['role'] = $account['role'];
        } else {
            // If the user is not remembered redirect to the login page.
            header('Location: ' . $redirect_file);
            exit;
        }
    } else if (!isset($_SESSION['loggedin'])) {
        // If the user is not logged in redirect to the login page.
        header('Location: ' . $redirect_file);
        exit;
    }
}
// Send activation email function
function send_activation_email($email, $code) {
    $subject = 'Account Activation Required';
    $headers = 'From: ' . mail_from . "\r\n" . 'Reply-To: ' . mail_from . "\r\n" . 'Return-Path: ' . mail_from . "\r\n" . 'X-Mailer: PHP/' . phpversion() . "\r\n" . 'MIME-Version: 1.0' . "\r\n" . 'Content-Type: text/html; charset=UTF-8' . "\r\n";
    $activate_link = activation_link . '?email=' . $email . '&code=' . $code;
    $email_template = str_replace('%link%', $activate_link, file_get_contents('activation-email-template.html'));
    mail($email, $subject, $email_template, $headers);
}
?>

CodePudding user response：

To perform auto login after registration you need to follow these steps:

1. Make sure you start the session. As I can see, you are already starting the session in main.php which is then included in register.php
2. After successful registration you need to populate the session variables in exactly the same way as you would do after successful login. You can receive the auto-generated ID by calling lastInsertId() method. The username comes from the form. The role is the default one, so you can hardcode it or read from database.

   // Username doesn't exist, insert new account
   $stmt = $pdo->prepare('INSERT INTO accounts (username, password, email, activation_code) VALUES (?, ?, ?, ?)');
   // We do not want to expose passwords in our database, so hash the password and use password_verify when a user logs in.
   $password = password_hash($_POST['password'], PASSWORD_DEFAULT);
   $uniqid = account_activation ? uniqid() : 'activated';
   $stmt->execute([ $_POST['username'], $password, $_POST['email'], $uniqid ]);
   
   // Login in the user
   session_regenerate_id();
   $_SESSION['loggedin'] = TRUE;
   $_SESSION['name'] = $_POST['username'];
   $_SESSION['id'] = $pdo->->lastInsertId();
   $_SESSION['role'] = 'the default role';
   
   if (account_activation) {
       // Account activation required, send the user the activation email with the "send_activation_email" function from the "main.php" file
       send_activation_email($_POST['email'], $uniqid);
       echo 'Please check your email to activate your account!';
   } else {
       header('Location: home.php');
       exit;
   }
   

3. In the above example, I added header('Location: home.php'); after successful registration. Adjust it according to your needs. Once the session variables are populated, you can redirect the user to the home page where the check for isset($_SESSION['id']) should take place. This will tell you whether the user is logged in or not.

I am not sure what is the purpose of $_SESSION['loggedin'] as it seems to be true in all cases. Maybe you can remove it from your code.