prepare("INSERT INTO users (username, email, password_hash) VALUES (?, ?, ?)"); $stmt->execute([$username, $email, $hash]); $_SESSION['user_id'] = db()->lastInsertId(); header('Location: ../index.php'); exit; } catch (Exception $e) { $error = "Registration failed: " . $e->getMessage(); } } else { $error = "Please fill all fields."; } } ?>