PHP curl: CURLOPT_URL, CURLOPT_POST, and CURLOPT_POSTFIELDS
The difference between POST and GET is how the server retrieves the data. As you have set CURLOPT_POST to true, the server normally receives the parameters via the CURLOPT_POSTFIELDS value (i.e. the parameters in the HTTP body) and presumably ignore the parameters sent in the URL string - but that really depends on the individual server.