Wordpress Archive Page - Get related taxonomies

Question

Im currently building filters for my archive pages. Since I'm working on an ecommerce project (woocommerce) I using some additional custom terms like brands. Considering a user is on the product category archive T-Shirts, I now want to display all brands in the archive page which are related to T-Shirts.

With get_terms I can only display all brands, but not "cross-filtered" by T-Shirts. Any help is well appreciated. I also might be totally wrong with my approach.

My approach until now: (This cant be a common way)

$product_ids = get_posts(array(
    'numberposts'   => -1, // get all posts.
    'post_type'     => 'product',
    'post_status'   => 'publish',
    'tax_query'     => array(
        array(
            'taxonomy'  => 'product_cat',
            'field'     => 'term_id',
            'terms'     => $term_id,
        ),
    ),
    'fields'        => 'ids', // Only get post IDs
));

foreach ($product_ids as $test_id) {
    $aaa = wp_get_post_terms($test_id, 'manufacturer', array('fields' => 'ids'));
    $brands[] = $aaa[0];
}

$brands = array_unique($brands);

Answer 1

I'm having trouble figuring out what "brands" is. Your wp_get_post_terms statement is going to get all the posts for each category in taxonomy "manufacturer." If manufacturer = brands, you can add this loop to cycle through them:

foreach ($product_ids as $test_id) { 
$post = get_post($test_id); 
echo '>> ' . $post->post_name . '</br>'; 
$aaa = wp_get_post_terms($test_id, 'manufacturer', 
    array('fields' => 'id=>slug'));

foreach( $aaa as $a) {
    echo $a . '</br>';
    }

}

You can then add 'if' statements to make your comparisons.