Top commented posts 30 days

<?php
global $post;
function filter_where($where = '') {
$where .= " AND post_date > '" . date('Y-m-d', strtotime('-30 days')) . "'";
return $where;}
add_filter('posts_where', 'filter_where');
query_posts('post_type=post&posts_per_page=5&orderby=comment_count&order=DESC);
while (have_posts()): the_post();
$thumb = get_the_post_thumbnail($post->ID,array(100,60), true);?>
<div class="relatedpost">
<div class="thumb"><?php echo $thumb; ?></div>
<div class="rtitle"><a href="<?php the_permalink(); ?>"title="<?php the_title(); ?>"><?php the_title(); ?></a></div>
</div>
<?php
endwhile;
wp_reset_query();
?>