I am using PHP with ripcord as suggested in the documentation.  Here is my code:

$url = 'url';

$db = 'xyzzy-sandbox2-12553485';

$username = "username";

$password = 'apikey';

require_once('ripcord.php');

$common = ripcord::client("$url/xmlrpc/2/common");

$uid = $common->authenticate($db, $username, $password, array());

echo json_encode($uid);

die;

This is a sandbox account.   The url is the url for my sandbox account.  It would not let me post the link.  I have a valid active username and have tried an api key and the username's password.  All I ever get is false for the $uid.  Any suggestions?