private static function cecf_call_data_url($data_url)
 {
     $user_key = base64_encode(CE_Plugin_Settings::get_user_key());
     //encode user key
     $output = null;
     try {
         //use cURL to contact server and get response with data
         $ch = curl_init($data_url);
         curl_setopt($ch, CURLOPT_HTTPHEADER, array('UserKey:' . $user_key));
         curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
         $output = curl_exec($ch);
         $output1 = curl_close($ch);
         $output = simplexml_load_string($output);
     } catch (Exception $e) {
         trigger_error("Unable to retrieve information from data source.");
     }
     return $output;
 }