Wednesday, December 18, 2013

Wordpress: Get tags related to category/categories

I found a function on wprecipes.com (and in the support forum somewhere) that helps in filtering the tag cloud to show only the tags of a certain or selected categories.

I copy it here, so I can find it easily the next time I need it, and also because it didn't work in a multisite installation. (Solution for that at the end)

This is the function you have to insert in your theme's functions.php:

 function get_category_tags($args) {  
      global $wpdb;  
      $tags = $wpdb->get_results  
      ("  
           SELECT DISTINCT terms2.term_id as tag_id, terms2.name as tag_name, null as tag_link  
           FROM  
                wp_posts as p1  
                LEFT JOIN wp_term_relationships as r1 ON p1.ID = r1.object_ID  
                LEFT JOIN wp_term_taxonomy as t1 ON r1.term_taxonomy_id = t1.term_taxonomy_id  
                LEFT JOIN wp_terms as terms1 ON t1.term_id = terms1.term_id,  
                wp_posts as p2  
                LEFT JOIN wp_term_relationships as r2 ON p2.ID = r2.object_ID  
                LEFT JOIN wp_term_taxonomy as t2 ON r2.term_taxonomy_id = t2.term_taxonomy_id  
                LEFT JOIN wp_terms as terms2 ON t2.term_id = terms2.term_id  
           WHERE  
                t1.taxonomy = 'category' AND p1.post_status = 'publish' AND terms1.term_id IN (".$args['categories'].") AND  
                t2.taxonomy = 'post_tag' AND p2.post_status = 'publish'  
                AND p1.ID = p2.ID  
           ORDER by tag_name  
      ");  
      $count = 0;  
      foreach ($tags as $tag) {  
           $tags[$count]->tag_link = get_tag_link($tag->tag_id);  
           $count++;  
      }  
      return $tags;  
 }  

You can use it in your theme files like this:

 $args = array('categories' => '12,13,14');  
 $tags = get_category_tags($args);  

As I mentioned this didn't work in a multisite install as the mysql database table names were differen. I had to change every instance of wp_ to wp_4_ in the function to make it work...

Source: http://www.wprecipes.com/wordpress-trick-function-to-get-tags-related-to-category