Get child product categories from parent product category in WooCommerce

Question

In WooCommerce, I am trying to get all child product category terms from the parent term id of the current product category with the code below:

$category = get_queried_object();
$category_parent_id = $category->parent;
$category_test = get_terms( ['taxonomy' => 'product_cat', 'hide_empty' => false] );

The variable $category_parent_id returns the parent product category id and $category_test returns all product category terms

I'm trying to return all child product categories using the parent product category term id retrieved from $category->parent

Logically I tried:

$category_test = $category_parent_id->get_terms( ['taxonomy' => 'product_cat', 'hide_empty' => false] );

and

$category_test = $category->parent->get_terms( ['taxonomy' => 'product_cat', 'hide_empty' => false] );

But this didn't give me back all child categories of the current parent category. Anyone have any idea if and if so how this can be achieved?

Answer 1

Edited (1)

You will need to use 'child_of' from WP_Term_Query available arguments, that will let you to get all child terms for the current product category parent term:

// Only on product category archive pages
if( is_product_category() ) {
    $main_term = get_queried_object();

    $args_query = array(
        'taxonomy' => 'product_cat', 
        'hide_empty' => false, 
        'child_of' => $main_term->parent
    );

    if ( $main_term->parent != 0 ) {
        // Loop through WP_Term Objects
        foreach ( get_terms( $args_query ) as $term ) {
            if( $term->term_id != $main_term->term_id ) {
                // $term->slug; // Slug

                // Output each (linked) term name…
                echo sprintf( '<a href="%s">%s</a></br>', get_term_link( $term->term_id, 'product_cat' ), $term->name );
            }
        }
    }
}

Or you can also use get_term_children() like:

// Only on product category archive pages
if( is_product_category() ) {
    $main_term  = get_queried_object();
    $taxonomy   = 'product_cat';

    if ( $main_term->parent != 0 ) {
        $child_ids = get_term_children( $main_term->parent, $taxonomy );

        echo '<ul>';

        foreach ( $child_ids as $child_id ) {
            if( $child_id != $main_term->term_id ) {
                $term = get_term_by( 'id', $child_id, $taxonomy );
                echo '<li><a href="' . get_term_link( $child_id, $taxonomy ) . '">' . $term->name . '</a></li>';
            }
        }
        echo '</ul>';
    }
}

This is only for product category archive pages, as for product pages you can have many product categories set for a product and the code will be complicated and quiet different…