public static function getPageRank($url = false)
    {
        // Composer autoloads classes out of the SEOstats namespace.
        // The custom autolader, however, does not. So we need to include it first.
        if(!class_exists('\GTB_PageRank')) {
            require_once realpath(__DIR__ . '/3rdparty/GTB_PageRank.php');
        }

        $gtb = new \GTB_PageRank(parent::getUrl($url));
        $result = $gtb->getPageRank();

        return $result != "" ? $result : static::noDataDefaultValue();
    }