Sulu\Bundle\PreviewBundle\Websocket\PreviewMessageHandler::start PHP Method

    private function start(MessageHandlerContext $context, $message)
    {
        if ($context->has('previewToken') && $this->preview->exists($context->get('previewToken'))) {
            $this->preview->stop($context->get('previewToken'));
        }
        $token = $this->preview->start($message['class'], $message['id'], $message['user'], $message['webspaceKey'], $message['locale'], $message['data'] ?: []);
        $response = $this->preview->render($token, $message['webspaceKey'], $message['locale']);
        $context->set('previewToken', $token);
        $context->set('locale', $message['locale']);
        return ['command' => 'start', 'token' => $token, 'response' => $response, 'msg' => 'OK'];
    }