private function extractLanguageCodesFromSolrResult( $solrResults )
    {
        $languages = array();

        if ( isset( $solrResults['response']['docs'] ) )
        {
            foreach ( $solrResults['response']['docs'] as $doc )
            {
                if ( isset( $doc['meta_language_code_ms'] ) )
                {
                    $languages[] = $doc['meta_language_code_ms'];
                }
            }
        }

        return $languages;
    }