WooCommerce Subscriptions - Get related orders Ids for a specific subscription

Updated: Added WooCommerce version 3+ Compatibility

It's very easy to get the order ID from subscription object. I am going to select, just like you, all subscriptions where 'post status' = 'wc-active' from post table.

// Get all customers subscriptions$customer_subscriptions = get_posts( array(    'numberposts' => -1,    // 'meta_key'    => '_customer_user',    // 'meta_value'  => get_current_user_id(), // Or $user_id    'post_type'   => 'shop_subscription', // WC orders post type    'post_status' => 'wc-active' // Only orders with status "completed") );// Iterating through each post subscription objectforeach( $customer_subscriptions as $customer_subscription ){    // The subscription ID    $subscription_id = $customer_subscription->ID    // IMPORTANT HERE: Get an instance of the WC_Subscription Object    $subscription = new WC_Subscription( $subscription_id );    // Or also you can use    // wc_get_order( $subscription_id );     // Getting the related Order ID (added WC 3+ comaptibility)    $order_id = method_exists( $subscription, 'get_parent_id' ) ? $subscription->get_parent_id() : $subscription->order->id;    // Getting an instance of the related WC_Order Object (added WC 3+ comaptibility)    $order = method_exists( $subscription, 'get_parent' ) ? $subscription->get_parent() : $subscription->order;    // Optional (uncomment below): Displaying the WC_Subscription object raw data    // echo '<pre>';print_r($subscription);echo '</pre>';}

You can also uncomment in the post query the 'meta_key' and 'meta_value' array lines to get the subscriptions for one customer… This code is tested and works

The most important thing here is:

$subscription = new WC_Subscription($customer_subscription->ID);

…as you will get the WC_Subscription object in which you can apply all WC_Subscription methods without getting errors, with for example:

$subscription = new WC_Subscription($post_id);$relared_orders_ids_array = $subscription->get_related_orders();