Call to undefined function App\Presenters\callback()

Dobrý deň kontaktný formulár som vytvoril len pri akcii mi vypisuje chybu Call to undefined function App\Presenters\callback() Vypisuje mi to pri novej verzii nette. Viete mi poradiť. Ďakujem

$form->onSuccess[] = callback($this, 'contactFormSubmitted');

protected function createComponentContactForms() {
$form = new UI\Form();
$form->addText('meno', 'Meno:', '15', '15')
->addRule(UI\Form::FILLED, 'Vyplnte Vase meno');
$form->addText('email', 'E-mail:')
->setEmptyValue('@')
->addRule(UI\Form::FILLED, 'Vyplnte email!')
->addRule($form::EMAIL, 'Nespravny format emailu!');

$form->addTextArea('sprava', 'Sprava:', 55, 10)
->addRule(UI\Form::FILLED, 'Vyplnte spravu');

$form->addSubmit('create', 'Odoslat');

$form->onSuccess[] = callback($this, 'contactFormSubmitted');
return $form;
}

public function contactFormSubmitted(Form $form) {
try {
$this->sendMail($form->getValues());
$this->flashMessage('Kontaktny formular uspesne odoslany!');
$this->redirect('this');
} catch (\Nette\InvalidStateException $e) {
$form->addError('Chyba pri odosielani prosim vyskusajte neskor.');
}
}

/** @var \Nette\Mail\IMailer @inject */
  public $mailer;
private function sendMail($values) {
$mail = new Message;
$mail->setSubject('Nova sprava');
$mail->setFrom($values['email'], $values['meno']);
$mail->addTo('urobweb@gmail.com');
$this->mailer->send($mail);
}