Fix existing function (or create new one) to store ID of parent product category as custom field on order in woocommerce

I've got a function which should get the slug of the first line item's parent category when an order is placed. A query is run to get the custom post type which has a matching slug, then the order should be updated with the ID of the matching custom post in a custom field called 'store_id' The function that I'm using is as follows but it's not working. I need it fixing asap! function add_store_id( $order_id){ global $woocommerce; global $post; if ( !$order_id ) return; // Get Category for order $order = new WC_Order($order_id); $items = $order->get_items(); foreach ( $items as $item ) { $product_id = $item['product_id']; $terms = get_the_terms( $product_id, 'product_cat', array( 'parent' => 0 ) ); foreach ( $terms as $term ) { $term = get_term_by("id", $term->parent, "product_cat"); if ($term->parent > 0) { $term = get_term_by("id", $term->parent, "product_cat"); } $cat_obj = get_term($term->term_id, 'product_cat'); $product_cat_slug = $cat_obj->name; break; } //Update order with ID of store. $the_query = new WP_Query(array('post_type'=>'stores','name'=>$product_cat_slug)); while ( $the_query->have_posts() ) : $the_query->the_post(); update_post_meta( $order_id, 'store_id', $post->ID); endwhile; wp_reset_postdata(); } } add_action('woocommerce_checkout_update_order_meta','add_store_id', 10, 2);