<?php
include('wp-load.php');
$nike = get_term_by('slug','nike','brand'); // This here just to illustrate
$terms = get_cross_referenced_terms(array(
'post_type' => 'product',
'related_taxonomy' => 'brand',
'term_id' => $nike->term_id,
));
foreach($terms as $term) {
echo "<p>{$term->name}</p>";
}
function get_cross_referenced_terms($args) {
global $wpdb;
$args = wp_parse_args($args,array(
'post_type' => 'post',
'taxonomy' => 'category',
'related_taxonomy' => 'post_tag',
'term_id' => 0,
));
extract($args);
$sql = <<<SQL
SELECT DISTINCT
{$wpdb->terms}.*,
COUNT(*) AS post_count
FROM
{$wpdb->terms}
INNER JOIN {$wpdb->term_taxonomy} ON {$wpdb->terms}.term_id={$wpdb->term_taxonomy}.term_id
INNER JOIN {$wpdb->term_relationships} ON {$wpdb->term_taxonomy}.term_taxonomy_id={$wpdb->term_relationships}.term_taxonomy_id
INNER JOIN {$wpdb->posts} ON {$wpdb->term_relationships}.object_id={$wpdb->posts}.ID
INNER JOIN {$wpdb->term_relationships} related_relationship ON {$wpdb->posts}.ID=related_relationship.object_id
INNER JOIN {$wpdb->term_taxonomy} related_term_taxonomy ON related_relationship.term_taxonomy_id=related_term_taxonomy.term_taxonomy_id
INNER JOIN {$wpdb->terms} related_terms ON related_term_taxonomy.term_id=related_terms.term_id
WHERE 1=1
AND (related_term_taxonomy.taxonomy<>{$wpdb->term_taxonomy}.taxonomy OR related_terms.term_id<>{$wpdb->terms}.term_id)
AND {$wpdb->posts}.post_type='%s'
AND {$wpdb->term_taxonomy}.taxonomy='%s'
AND related_term_taxonomy.taxonomy='%s'
AND related_terms.term_id=%d
GROUP BY
{$wpdb->terms}.term_id
SQL;
$sql = $wpdb->prepare($sql,$post_type,$taxonomy,$related_taxonomy,$term_id);
$terms = $wpdb->get_results($sql);
return $terms;
}
