private static function loadContent($url) {
        //TODO: implement URL content load functionality with CURL and proxy

        $ch = curl_init($url);
        $options = array(
            CURLOPT_RETURNTRANSFER => true
        );
        curl_setopt_array($ch, $options);

        $content = curl_exec($ch);

        curl_close($ch);

        if ($content === false) {
            throw new Exception("Can't get content from " . $url);
        }
        return $content;
    }