Contao\CoreBundle\Framework\ContaoFramework::handleRequestToken PHP Method

    private function handleRequestToken()
    {
        /** @var RequestToken $requestToken */
        $requestToken = $this->getAdapter(RequestToken::class);
        // Deprecated since Contao 4.0, to be removed in Contao 5.0
        if (!defined('REQUEST_TOKEN')) {
            define('REQUEST_TOKEN', $requestToken->get());
        }
        if ($this->canSkipTokenCheck() || $requestToken->validate($this->request->request->get('REQUEST_TOKEN'))) {
            return;
        }
        if ($this->request->isXmlHttpRequest()) {
            throw new AjaxRedirectResponseException($this->router->generate('contao_backend'));
        }
        throw new InvalidRequestTokenException('Invalid request token. Please reload the page and try again.');
    }