ToolbarListener.php

    /**
     * ProfilerEvent::EVENT_COLLECTED event callback.
     *
     * @param ProfilerEvent $event
     */
    public function onCollected(ProfilerEvent $event)
    {
        $application = $event->getApplication();
        $request     = $application->getRequest();

        if ($request->isXmlHttpRequest()) {
            return;
        }

        $response = $application->getResponse();
        $headers = $response->getHeaders();
        if ($headers->has('Content-Type')) {
            if (true === strpos($headers->get('Content-Type')->getFieldValue(), 'html')) {
                $this->injectToolbar($event);
            } elseif (true === strpos($headers->get('Content-Type')->getFieldValue(), 'json')) {
                $this->injectJsonToolbar($event);
            }
        }

        // todo: X-Debug-Token logic?
        // todo: redirect logic


    }

    /**
     * Tries to injects the toolbar into the view. The toolbar is only injected in well
     * formed Json by replacing the closing }, leaving ESI untouched.
     *
     * @param ProfilerEvent $event
     */
    protected function injectJsonToolbar(ProfilerEvent $event)
    {
        $entries     = $this->renderEntries($event);
        $response    = $event->getApplication()->getResponse();;

        $toolbarView = new ViewModel(array('entries' => $entries));
        $toolbarView->setTemplate('zend-developer-tools/toolbar/toolbar');
        $toolbar     = $this->renderer->render($toolbarView);
        $toolbar     = str_replace("\n", '', $toolbar);

        $injected    = preg_replace('/}$/im', ', toolbar:"' . $toolbar . '"}', $response->getBody(), 1);

        $response->setContent($injected);
    }