public function log_in(){
      //print_r($this->input->post());
      $form_username=$this->input->post('username');
      $form_username=$this->input->post('password');
      if($form_username=='admin' && $form_password=='admin123'){
        session_start();
        $_SESSION['log_in']=true;
        $_SESSION['user']=$form_username;
        $data['message']='Kirjautuminen onnistui';
        $data['page']='book/info';
        $this->load->view('menu/content',$data);
      }