The PHP code example will execute a custom SQL Query in WordPress to get tags specific from categories. Simply add the function below in your theme’s functions.php file or somewhere in your custom page or plugin. It accepts multiple category ids as input parameter and then return an array of tags.
Also in this tutorial, I’ll show a similar way to display the list of tags.
[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 $tags;
}
[/php]
Usage Example
[php] <?php$args = array(
‘categories’ => ‘12,13,14’
);
$tags = get_category_tags($args);
$content .= "<ul>";
foreach ($tags as $tag) {
$content .= "<li><a href=\"$tag->tag_link\">$tag->tag_name</a></li>";
}
$content .= "</ul>";
echo $content;
?>
[/php]
Or, you can try with the code below:
[php] <?php$project_query = query_posts(‘category_name=projects’);
while (have_posts()) : the_post();
$posttags = get_the_tags();
if ($posttags) {
foreach($posttags as $tag) {
$all_tags_arr[] = $tag -> name; //USING JUST $tag MAKING $all_tags_arr A MULTI-DIMENSIONAL ARRAY, WHICH DOES WORK WITH array_unique
}
}
endwhile;
?>
<?php if ( is_array($all_tags_arr) && count($all_tags_arr) > 0 ): ?>
<?php
$tags_arr = array_unique($all_tags_arr); //REMOVES DUPLICATES
foreach( $tags_arr as $tag ):
$el = get_term_by(‘name’, $tag, ‘post_tag’);
$arr[] = ‘"tag-‘.$el->slug.’"’;
?>
<span><a href="#<?php echo $el->slug; ?>" id="taglink-tag-<?php echo $el->slug; ?>" rel="tag-<?php echo $el->slug; ?>"><?php echo $el->name; ?></a> <span class="slash">//</span></span>
<?php endforeach; ?>
<?php echo ‘<pre>’.print_r($tags_arr, true).'</pre>’;?>
[/php]
I copied the source code above from WordPress Support Get Tags specific to Category
