Hoping to persuade you to remove the PHP short tags in favor of of the long-hand/full/standard/whatever syntax.
<?=$var?> doesn't play nice everywhere. While my understanding is that PHP 5.4 will support it regardless of the
short_open_tag setting, WordPress itself only requires 5.2.4, so many users may not be running 5.4 yet. It's also discouraged by WordPress coding standards.
Oh, and I also through an isset() check in there so I'd stop getting a "headers already sent error" when debug is on.
Or if diffs aren't your thing, here's a zip.