WooCommerce 3.0+
you can get the order items of an order by
$order = wc_get_order( $order_id );
$items = $order->get_items();
then if you loop through the items, you can get all the relevant data:
foreach ( $items as $item ) {
$product_name = $item->get_name();
$product_id = $item->get_product_id();
$product_variation_id = $item->get_variation_id();
}
a good tip is to check how the admin order pages get the data, you’ll find many answers there!
Pre-WooCommerce 3.0
$order = new WC_Order( $order_id );
$items = $order->get_items();
foreach ( $items as $item ) {
$product_name = $item['name'];
$product_id = $item['product_id'];
$product_variation_id = $item['variation_id'];
}