How to Implement 'Remember Me' Functionality in a PHP Login System for Enhanced User Experience?

PHP Login System with "Remember Me" Functionality [Duplicate]

To enhance the user experience, you can implement a "remember me" feature in your PHP login system, allowing users to stay logged in across multiple sessions.

Secure Cookie Storage

The best practice for storing a persistent cookie is to use a separate table in the database called auth_tokens:

CREATE TABLE `auth_tokens` (
    `id` integer(11) not null UNSIGNED AUTO_INCREMENT,
    `selector` char(12),
    `token` char(64),
    `userid` integer(11) not null UNSIGNED,
    `expires` datetime,
    PRIMARY KEY (`id`)
);

After Login

Upon login, generate unique random values for selector and token:

if ($login->success && $login->rememberMe) {
    $selector = base64_encode(random_bytes(9));
    $authenticator = random_bytes(33);

    setcookie(
        'remember',
        $selector . ':' . base64_encode($authenticator),
        time() + 864000, // 10 days
        '/',
        'yourdomain.com',
        true, // TLS-only
        true  // http-only
    );

    // Insert data into the database
    $database->exec(
        "INSERT INTO auth_tokens (selector, token, userid, expires) VALUES (?, ?, ?, ?)",
        [
            $selector,
            hash('sha256', $authenticator),
            $login->userId,
            date('Y-m-d\TH:i:s', time() + 864000)
        ]
    );
}

Re-Authentication

if (empty($_SESSION['userid']) && !empty($_COOKIE['remember'])) {
    list($selector, $authenticator) = explode(':', $_COOKIE['remember']);

    // Retrieve row from the database
    $row = $database->selectRow(
        "SELECT * FROM auth_tokens WHERE selector = ?",
        [
            $selector
        ]
    );

    // Verify hash and set session
    if (hash_equals($row['token'], hash('sha256', base64_decode($authenticator)))) {
        $_SESSION['userid'] = $row['userid'];
        // Regenerate a login token as per previous example
    }
}

Details

• The selector provides 36 bits of collision resistance, preventing brute force attacks.
• The authenticator provides ample unpredictability with 264 bits of randomness.
• The hash mitigates impersonation risks after potential information leaks.
• Hashing with hash_equals() prevents timing attacks.
• Separating selector and authenticator optimizes database lookups.

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