I'm trying to add a user (by variable $id) to a Twitter List using PHP CURL, and I can't get it to work.

$curl_handle = curl_init();

curl_setopt($curl_handle, CURLOPT_URL, "http://twitter.com/username/list/members.xml");

curl_setopt($curl_handle, CURLOPT_POST, 1);

curl_setopt($curl_handle, CURLOPT_POSTFIELDS, "id=$id");

curl_setopt($curl_handle, CURLOPT_CONNECTTIMEOUT, 2);

curl_setopt($curl_handle, CURLOPT_RETURNTRANSFER, 1);

curl_setopt($curl_handle, CURLOPT_USERPWD, "username:password");

curl_setopt($curl_handle, CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_1_1);

curl_setopt($curl_handle, CURLOPT_VERBOSE, 1);

$result = curl_exec($curl_handle);

// Look at the returned header

$resultArray = curl_getinfo($curl_handle);

curl_close($curl_handle);

if($resultArray['http_code'] == "200"){

   echo 'Success';

} else {

   echo var_dump($resultArray);

}

The var_dump reveals that the http_code of the return is 403.