session_start();// Login config$USER = "admin";$PASS = "admin123";if (!isset($_SESSION['logged_in'])) { if ($_SERVER['REQUEST_METHOD'] == 'POST') { if ($_POST['username'] === $USER && $_POST['password'] === $PASS) { $_SESSION['logged_in'] = true; header("Location: " . $_SERVER['PHP_SELF']); exit; } else { $error = "Login gagal!"; } } echo ' <!DOCTYPE html>