JS slideshow "nextPhoto"/"prevPhoto" not working
<p>I'm working on a JavaScript slideshow someone else originally built, and I seem to have busted it. The "previous" and "next" buttons don't work - they don't do anything, actually. </p>

<p>Using the HTML Validator plugin for Firefox when I load the page, I get an error message: "Undefined variable: random_photo in [filename.php]"</p>

<p>When I click on "next" or "previous", I get an additional error: "nextPhoto is not defined"</p>

<p>I have compared the code on this page to another existing (and functional) slideshow, and I cannot find any differences. </p>

<p>I'm happy to pup up code snippets, but I'm not sure what's relevant...I'm kind of a newbie to JavaScript.</p>

<p>What am I missing/what can I do to define the supposedly undefined variables?</p>
