Working on a new plug-in but getting cURL error: Couldn't resolve host

class Sb_metascore
    {

      var $return_data = "";

      function Sb_metascore()
      {
              global $TMPL;

            // $target_url = "http://www.metacritic.com/games/platforms/pc/imperiumromanum/"; // <- does work
            $target_url =  $TMPL->fetch_param('url'); // <- doesn't work
            $userAgent = 'Googlebot/2.1 (http://www.googlebot.com/bot.html)';

            // make the cURL request to $target_url
            $ch = curl_init();
            
            curl_setopt($ch, CURLOPT_USERAGENT, $userAgent);
            curl_setopt($ch, CURLOPT_URL,$target_url);
            curl_setopt($ch, CURLOPT_FAILONERROR, true);
            curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
            curl_setopt($ch, CURLOPT_AUTOREFERER, true);
            curl_setopt($ch, CURLOPT_RETURNTRANSFER,true);
            curl_setopt($ch, CURLOPT_TIMEOUT, 10);
            
            $html= curl_exec($ch);
            if (!$html) {
                echo "
            cURL error number: " .curl_errno($ch);
                echo "
            cURL error: " . curl_error($ch);
                exit;
            }

            // parse the html into a DOMDocument
            $dom = new DOMDocument();
            @$dom->loadHTML($html);

            // grab the score
            $xpath = new DOMXPath($dom);
            $imgs = $xpath->evaluate("/html/body/div[2]/div[3]/table/tr[2]/td[2]/table[3]/tr/td[2]/table/tr/td/table/tr[2]/td[1]/img");

            for ($i = 0; $i < $imgs->length; $i++) {
                $img = $imgs->item($i);
                $alt = $img->getAttribute('alt');
                $score = preg_replace('/Metascore: /si', '', $alt);
                //echo "$score";
                return $this->return_data = $score;
            }    
      }
      // END FUNCTION