redirect()->to() doesn't work in controller __construct()

Hi,

why redirect()->to() doesn't work in controller __construct()??

some options?

I need to put the redirect()->to() in the method

public function __construct()
    {
        helper('admin_auth');

        if(comprovacio_auth_usuari() == false)
        {
            return redirect()->to('/admin/login');
        }
    }

    public function dashboard()
    { 
        $session = session();
        $auth_user = $session->get('auth_user');

        $data['idioma'] = comprovacio_idioma_usuari();
        $data['auth_user'] = (object)$auth_user;
        $data['opc'] = OPC_DASHBOARD;

        echo view('admin/layouts/html_start', $data);
echo view('admin/layouts/head');
echo view('admin/layouts/body_start');
        echo view('admin/layouts/sidebar');
       
echo view('admin/pages/dashboard');

        echo view('admin/layouts/footer');
echo view('admin/layouts/html_end');
    }


thanks,

Andreu.