dual-taxonomy-shortcode.php

// ================================================================================================
// FLIPPING THE GET SHORTCODE TO GET CATS IN A RESTRICTED FASHION ^CW
// ================================================================================================

/**
 *   Eg : [getcats type="slug"]
 *   Shortcode for getting a list of categories from a current product category & restricted by product brand
 *  
 *   Shortcode attributes : 
 *   type (optional): type of resultset values returned (slug or id) Default: slug  
 * 
 *   returns comma-separated string of brand slugs or brand ids
 */
function get_category_from_brands( $atts )
{
    $current_category = get_queried_object();
    $res_cats = array();
	$type = ( $atts['type'] == 'id' ) ? 'term_id' : 'name';
    if ( $current_category instanceof WP_Term ) {
        
        // get all deepest level of childs slug
        $childrens = get_deepest_level_childs( $current_category );
        foreach ( $childrens as $child ) {
            
            // Get all products under specified product category slug (taxonomy)
            $post_args = array(
                'posts_per_page' => -1,
                'post_type' => 'product',
                'tax_query' => array(
                    array(
                        'taxonomy' => 'product_cat',
                        'field' => 'slug',
                        'terms' => $child,
                    )
                )
            );
            $posts_array = get_posts( $post_args );

            if ( empty( $posts_array ) ) {
                continue;
            }

            // Get all post ids
            $post_ids = array_column( $posts_array, 'ID' );

            // Get all tabs for above post ids
            $post_args_2 = array(
                'posts_per_page' => -1,
                'post_type' => 'product',
				'post__in' => $post_ids,
                'tax_query' => array(
                    array(
                        'taxonomy' => 'pa_brandname',
                        'field' => 'slug',
                        'terms' => $_GET["brand"],
                    )
                )
            );
            $ids_filtered = array_column( $posts_array, 'ID' );
                
            // If no brands were found for all above posts under given category
            if ( !empty( $ids_filtered ) ) {
				if ( $type === "term_id" ) {
					$res_cats[] = get_term_by( "slug", $child, "product_cat" )->term_id;
				} else {
					$res_cats[] = $child;
				}
            }
        }
		
		$terms_direct = array_column( get_terms(
			'product_cat',
			array(
				'parent' => $current_category->term_id,
			)
		), "slug" );
		
		$res_cats = array_diff( $res_cats, array_diff( $res_cats, $terms_direct ) );

    }
    
    $result = implode( ',', $res_cats );
    return $result;
}
add_shortcode('getcats', 'get_category_from_brands');