Undefined offset . How to rid this error?

[eluser]CI-Newb[/eluser]
Excellent, thank you both for the replies. How does this look now:

Code:

$parts = explode("-", $code);
        if (count($parts) != 2) {
            $code = NULL;
            $userid = NULL;
        } else {
            $code = $parts[0];
            $userid = $parts[1];
        }

if both parts are not present set both to null which my check will then redirect to the error page. otherwise set them both to the appropriate variables