Get the Connected Taxonomies in WordPress

connected_taxonomies

//	Get the Connected Taxonomies via Posts
function get_the_connected_taxonomies($tax_name, $rel_tax_type = 'post_tag', $tax_type = 'category', $post_type = 'post', $from_cache = true, $search_key = 'slug') {

	//	Transient Key
	$transient_key = $post_type . '-' . $rel_tax_type . '-' . $tax_type . '-' . $tax_name . '-cache';

	//	Check
	if($from_cache && get_transient($transient_key)) {

		//	Return
		return get_transient($transient_key);
	}

	//	Tax Lists
	$tax_lists = array();

	//	Query the Posts
	$query = new WP_Query(array(
		'post_type' => $post_type,
		'post_status' => 'publish',
		'tax_query' => array(
			array(
				'taxonomy' => $tax_type,
				'field'    => $search_key,
				'terms'    => $tax_name,
			)
		)
	));

	//	Loop Posts in Taxonomy
	foreach($query->posts as $post) {

		//	Get the Taxonomies
		$the_taxs = get_the_terms($post->ID, $rel_tax_type);

		//	Check
		if($the_taxs) {

			//	Loop Each
			foreach($the_taxs as $the_tax) {

				//	Check
				if(!isset($tax_lists[$the_tax->term_id])) {

					//	Store Taxonomy
					$tax_lists[$the_tax->term_id] = $the_tax;
				}
			}
		}
	}

	//	Check
	if(sizeof($tax_lists) > 0) {

		//	Set Transient for 30 minutes
		set_transient( $transient_key, $tax_lists, 60 * 30 );
	}

	//	Return
	return $tax_lists;
}