wordpress 由分类找到 关联的标签–函数运用

用于在选定wordpress栏目分类后，显示相关的标签，如下写这个函数及调用呢？如下：

/////////////分类-标签关联函数/////////////////////////
function ludou_get_category_tags($args) {
	global $wpdb;
	$tags = $wpdb->get_results
	("
		SELECT DISTINCT terms2.term_id as tag_id, terms2.name as tag_name
		FROM
			$wpdb->posts as p1
			LEFT JOIN $wpdb->term_relationships as r1 ON p1.ID = r1.object_ID
			LEFT JOIN $wpdb->term_taxonomy as t1 ON r1.term_taxonomy_id = t1.term_taxonomy_id
			LEFT JOIN $wpdb->terms as terms1 ON t1.term_id = terms1.term_id,
 
			$wpdb->posts as p2
			LEFT JOIN $wpdb->term_relationships as r2 ON p2.ID = r2.object_ID
			LEFT JOIN $wpdb->term_taxonomy as t2 ON r2.term_taxonomy_id = t2.term_taxonomy_id
			LEFT JOIN $wpdb->terms as terms2 ON t2.term_id = terms2.term_id
		WHERE
			t1.taxonomy = 'category' AND p1.post_status = 'publish' AND terms1.term_id IN (".$args['categories'].") AND
			t2.taxonomy = 'post_tag' AND p2.post_status = 'publish'
			AND p1.ID = p2.ID
		ORDER by tag_name
	");
	$count = 0;
	
	if($tags) {
	  foreach ($tags as $tag) {
	    $mytag[$count] = get_term_by('id', $tag->tag_id, 'post_tag');
	    $count++;
	  }
	}
	else {
	  $mytag = NULL;
	}
	
	return $mytag;
}
//------------------以下是调用-------------------------
// 12,13是分类ID，多个用半角逗号隔开
$args = array( 'categories' => '12,13');
 
// 调用上面定义的函数，来获取ID为12，13的分类的关联标签
$tags = ludou_get_category_tags($args);
 
// 输出我们获取到的关联标签，以列表形式打印
$content .= "<ul>";
 
if(!empty($tags)) {
  foreach ($tags as $tag) {
    $content .= "<li><a href="".get_tag_link($tag->term_id)."">".$tag->name."</a></li>";
  }
}
 
$content .= "</ul>";
echo $content;