Controllers\xAPI\DocumentController::index PHP Method

    public function index()
    {
        // Runs filters.
        if ($result = $this->checkVersion()) {
            return $result;
        }
        // Gets all documents.
        $documents = $this->document->all($this->getOptions(), $this->document_type, $this->getIndexData(['since' => ['string', 'timestamp']]));
        // Returns array of only the stateId values for each document.
        $ids = array_column($documents->toArray(), 'identId');
        return \Response::json($ids);
    }