public function isValidCallbackRequest()
    {
        if (!$this->isValidHubSignature()) {
            return false;
        }

        $decoded = $this->getDecodedBody();

        $object = isset($decoded['object']) ? $decoded['object'] : null;
        $entry = isset($decoded['entry']) ? $decoded['entry'] : null;

        return $object === 'page' && null !== $entry;
    }