function gu_callapi() {

  global $gu_request, $gu_response;

  $c_param = 0;
  foreach ($gu_request as $key => $value) {
    $value = urlencode($value);
    $c_param++;
    if ($c_param>1) { $req .= "&"; }
    $req .= "$key=$value"; }

  $curl_handle = curl_init();
  curl_setopt($curl_handle, CURLOPT_URL, "http://goodurl.de/lib/api.php");
  curl_setopt($curl_handle, CURLOPT_CONNECTTIMEOUT, 2);
  curl_setopt($curl_handle, CURLOPT_RETURNTRANSFER, 1);
  curl_setopt($curl_handle, CURLOPT_POST, 1);
  curl_setopt($curl_handle, CURLOPT_POSTFIELDS, $req);
  $buffer = curl_exec($curl_handle);
  curl_close($curl_handle);

  $result = explode("&", $buffer);
  if (count($result)==0) {
    return 0; }

  foreach ($result as $data) {
    $entry = explode("=", $data);
    $gu_response[$entry[0]]=$entry[1]; }
  return count($gu_response); }

$gu_request['cmd']="new_shorturl";
$gu_request['url']="http://www.beispiel.com/seite.html?param=wert";
$gu_request['user']="testuser";
$gu_request['pw']="geheim";

$result = gu_callapi();

if ($result==0) {
  echo "Fehler beim Aufruf der Funktion"; }
else if ($gu_response['error']<>0) {
  echo "von API zurüchgegebene Fehlernummer: ".$gu_response['error']; }
else {
  echo "erzeugte Kurz-Url: " . $gu_response['short']; }