class User {
  function save() {
    DB::exec('INSERT INTO User (username, password)', ['username' => $this->username, 'password' => $password);
    $this->id = PDO::lastInsertId();
  }

  function load($id) {
    DB::exec('SELECT * FROM User WHERE id = :id', ['id' => $id]);
    $data = DB::fetch();
    $this->id = $data['id'];
    $this->username = $data['id'];
    $this->password = $data['password'];
  }

  static function find($id) {
    return (new User())->load($id);
  }

  static function login($username, $password) {
    DB::exec('SELECT FROM User WHERE username = :username, password = PASSWORD(:password)', ['username' => $username, 'password' => $password]);
    $user = DB::fetch();
    if($user)
      $_SESSION['userId'] = $user->id;
  }

  static function logout() {
      unset($_SESSION['userId']);
  }
};