Display most popular tags of WordPress blog

 
<ul id="footer-tags">
    <?php $wpdb->show_errors(); ?> 
    <?php
        global $wpdb;
        $term_ids = $wpdb->get_col("
            SELECT term_id FROM $wpdb->term_taxonomy
            INNER JOIN $wpdb->term_relationships ON $wpdb->term_taxonomy.term_taxonomy_id=$wpdb->term_relationships.term_taxonomy_id
            INNER JOIN $wpdb->posts ON $wpdb->posts.ID = $wpdb->term_relationships.object_id
            WHERE DATE_SUB(CURDATE(), INTERVAL 30 DAY) <= $wpdb->posts.post_date");
 
if(count($term_ids) > 0){
 
  $tags = get_tags(array(
    'orderby' => 'count',
    'order'   => 'DESC',
    'number'  => 28,
    'include' => $term_ids,
  ));
 
foreach ( (array) $tags as $tag ) {
    echo '<li><a href="' . get_tag_link ($tag->term_id) . '" rel="tag">' . $tag->name . '</a></li>';
}
}
?>
</ul>