将当前HTML与PHP AJAX调用返回的数据进行比较

I'm having issues comparing current list items on a page with ones that are retrieved through a PHP AJAX refresh. I only want the box to refresh if there are new items.

The PHP returns a bunch of formatted, HTML list items.

<ul class="socialFeed twitterFeed">
    <script type="text/javascript">
        $(function() {
            refreshTweets();
        });
        function refreshTweets() {
            $.get("php/tweets.php", function(data){
                var current = $(".socialFeed.twitterFeed").html();
                if(current != data) {
                    $(".socialFeed.twitterFeed").hide().html(data).fadeIn();
                }
            });
        }
        setInterval("refreshTweets()", 2000);
    </script>
</ul>

I can't figure out why the string comparison isn't working. I'm missing something, but I'm not sure what.