Code-Snippets-Functions/Execute a function on a child site/WooCommerce/add-gtin-to-orders-order-emails.txt

// Utility function to get the GTIN code from the product object
function get_product_gtin_code( $product ) {
    return $product->get_meta('hwp_product_gtin');
}

// Utility function to get the GTIN label name
function get_gtin_label() {
    $label = get_option('hwp_gtin_text');
    return esc_html__( $label ? $label : 'GTIN');
}

// Save Product GTIN as custom order item and display it on orders (items) and emails
add_action( 'woocommerce_checkout_create_order_line_item', 'save_and_display_gtin_everywhere', 10, 4 );
function save_and_display_gtin_everywhere( $item, $item_key, $values, $order ) {
    if ( $gtin_code = get_product_gtin_code($values['data']) ) {
        $item->add_meta_data( 'gtin_code', $gtin_code );
    }
}

// Add readable "meta key" label name replacement
add_filter('woocommerce_order_item_display_meta_key', 'filter_wc_order_item_display_meta_key', 10, 3 );
function filter_wc_order_item_display_meta_key( $display_key, $meta, $item ) {
    if( $item->get_type() === 'line_item' && $meta->key === 'gtin_code' ) {
        $display_key = get_gtin_label();
    }
    return $display_key;
}

// Utility function to get the GTIN code from the order item object
function get_order_item_gtin_code( $item ) {
    return $item->get_meta('gtin_code');
}