quandl anonymous user limit exceeded

I'm getting the following error out of my php script when executed from my Digital Ocean Droplet

Error - QELx01 : You have exceeded the anonymous user limit of 50 calls per day. To make more calls today, please register for a free Quandl account and then include your API key with your requests.

However the call works fine when ran from local host.

I am using the api_key allocated by quandl

here is the my code snippet:

            // Silver 
            // Get newest date
            $api_key = "SBPYxUYb_hz32nKxtqGU"; 
            $params = new \stdClass();            
            $params->start_date = "2018-08-14";
            $params->end_date = "2018-08-14";            
            $params->access_key = $api_key;
            $json = CallAPI('GET', 'https://www.quandl.com/api/v3/datasets/LBMA/SILVER', $params , false);
            echo($json);
            $silver_data = json_decode($json, TRUE);

            // Gte Current Price                
            $params->start_date = $silver_data["dataset"]["newest_available_date"];
            $params->end_date   = $silver_data["dataset"]["newest_available_date"];            
            $params->access_key = $api_key;
            $json = CallAPI('GET', 'https://www.quandl.com/api/v3/datasets/LBMA/SILVER', $params , false);
            $silver_data = json_decode($json, TRUE);
            $silver_aud = $silver_data["dataset"]["data"][0][1] / $usdaud;

            function CallAPI($method, $url, $data = false, $key = false)
            // method: html request method
            // url: the web address
            // data: dat to append to url
            // key: the access key to the web site
            {
                $curl = curl_init();

                switch ($method)
                {
                    case 'POST':
                        curl_setopt($curl, CURLOPT_POST, 1);

                        if ($data)
                            curl_setopt($curl, CURLOPT_POSTFIELDS, $data);
                        break;

                    case 'PUT':
                        curl_setopt($curl, CURLOPT_PUT, 1);
                        break;

                    default:
                        if ($data)
                        {
                            $info = http_build_query($data);
                            $url = sprintf('%s?%s', $url, $info);
                        }
                }

                if ($key)
                {
                    $key_header = array('content-type: application/x-www-form-urlencoded', 'x-api-key: ' . $key);
                    curl_setopt($curl, CURLOPT_HTTPHEADER, $key_header);
                }

                // Optional Authentication:
                curl_setopt($curl, CURLOPT_HTTPAUTH, CURLAUTH_BASIC);
                curl_setopt($curl, CURLOPT_USERPWD, '');

                curl_setopt($curl, CURLOPT_URL, $url);
                curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);                

                $result = curl_exec($curl);

                $err = curl_error($curl);
                curl_close($curl);
                if ($err) 
                {
                    echo "curl Error :" . $err;
                }               

                return $result;
            }