Saving persistent data

No it is saved in your session. You need to initialize session first to use $this->persistent.

for example:

class DictionaryController extends \Phalcon\Mvc\Controller
{
    public function indexAction()
    {
        $this->persistent->testing_key = "my test value";
        $this->response->redirect("dictionary/show");
    }

    public function showAction()
    {
        $this->view->disable();
        echo "<pre>";
        print_r($_SESSION);
    }
}

you get

Array
(
    [_started] => 1
    [DictionaryController] => Array
        (
            [testing_key] => my test value
        )
)

Persistent makes Class name session key and add to it key=>value