WordPress trick: function to get tags related to category
by Jean-Baptiste Jung on October 12, 2009
First, here is the function you have to paste in your function.php file:
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;
}
Once you have pasted the function, you can use it in your theme:
$args = array('categories' => '12,13,14');
$tags = get_category_tags($args);
Credits: WordPress Codex
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WordPress trick: function to get tags related to category