You are getting the error because, at the time the script is running in those instances, $REQUEST['url'] and/or $REQUEST['method'] are not set. Whether or not they should always be set or not is a separate issue, which will require a decision on your part and possibly some additional validation code to avoid it. But if it's OK for them to not be set, then you can avoid the warning by doing:
$action = (isset($_REQUEST['url'])) ? $_REQUEST['url'] : '';
$method = (isset($_REQUEST['method'])) ? $_REQUEST['method'] : '';
The above will wet the variables to an empty string if the respective $_REQUEST element is not set. You could replace the empty quotes with a default value, if that would make more sense.