functions.php

<?php

// custom post type permalinks
add_filter('post_type_link', 'deb_permalink', 10, 4);
function deb_permalink($permalink, $post_id, $leavename) {
    if (strpos($permalink, '%taxonomy_name%') === FALSE) return $permalink;

    // Get post
    $post = get_post($post_id);
    if (!$post) return $permalink;

    // Get taxonomy terms
    $terms = wp_get_object_terms($post->ID, 'product_types');
    if (!is_wp_error($terms) && !empty($terms) && is_object($terms[0])) {
    	$taxonomy_slug = '';
		if ( $terms[0]->parent ) {
    		$taxonomy_slug .= $terms[1]->slug;
			$taxonomy_slug .= '/';
    	}
		$taxonomy_slug .= $terms[0]->slug;
    } else 
		$taxonomy_slug = 'other';
    return str_replace('%taxonomy_name%', $taxonomy_slug, $permalink);
}