copymailrpi/web/includes/auth.php

<?php

function auth_start(): void {
    if (session_status() === PHP_SESSION_NONE) {
        session_name('copymail_sess');
        session_start();
    }
}

function auth_check(): void {
    auth_start();
    if (empty($_SESSION['admin_id'])) {
        header('Location: /login.php');
        exit;
    }
}

function auth_login(string $username, string $password): bool {
    $st = db()->prepare('SELECT id, password FROM admin_users WHERE username = ? LIMIT 1');
    $st->execute([$username]);
    $row = $st->fetch();
    if ($row && password_verify($password, $row['password'])) {
        $_SESSION['admin_id']   = $row['id'];
        $_SESSION['admin_user'] = $username;
        return true;
    }
    return false;
}

function auth_logout(): void {
    auth_start();
    session_destroy();
    header('Location: /login.php');
    exit;
}

function current_user(): string {
    return $_SESSION['admin_user'] ?? '';
}