Validation

Because you are redirecting, killing your data.

PHP Code:

if($validation->run())
      {

          redirect()->to('user/pannello_user');

      } 


I think you can use withInput() but then you need to use the old() function as well or use the form_helper for everything.
https://codeigniter.com/user_guide/gener...l#redirect
https://codeigniter.com/user_guide/gener...s.html#old

Take a look at the tutorial.
https://codeigniter.com/user_guide/tutorial/index.html

PHP Code:

public function create()
{
    $model = new NewsModel();

    if ($this->request->getMethod() === 'post' && $this->validate([
            'title' => 'required|min_length[3]|max_length[255]',
            'body'  => 'required'
        ]))
    {
        $model->save([
            'title' => $this->request->getPost('title'),
            'slug'  => url_title($this->request->getPost('title'), '-', TRUE),
            'body'  => $this->request->getPost('body'),
        ]);

        echo view('news/success');

    }
    else
    {
        echo view('templates/header', ['title' => 'Create a news item']);
        echo view('news/create');
        echo view('templates/footer');
    }
}