public function onContentItem()
    {
        $this->initSession();
        /* blindly copied from Vickers' Rating demo app */
        $_SESSION[__CLASS__] = [
            'consumer_key' => $this->consumer->getKey(),
            'resource_id' => getGuid(),
            'resource_id_created' => false,
            'user_consumer_key' => $this->consumer->getKey(),
            'user_id' => 'System',
            'isStudent' => false,
            'isContentItem' => true,
            'lti_version' => $_POST['lti_version'],
            'return_url' => $this->return_url,
            'title' => postValue('title'),
            'text' => postValue('text'),
            'data' => postValue('data'),
            'document_targets' => $this->documentTargets
        ];

        $this->redirectURL = $this->assignRedirect('content-item');
    }