Woocommerce Subscriptions: get all subscribed products for a subscriber (find if a product is subscribed)

functions.php_snip

<?php
function has_an_active_subscriber( $product_id = null ){

    // Empty array to store ALL existing Subscription PRODUCTS
    $products_arr = array();


    $products_subscr = get_posts( array(
        'numberposts' => -1,
        'post_status' => 'publish',
        'post_type'   => array( 'product', 'product_variation' ),
        'meta_key' => '_subscription_price',
    ) );
    foreach( $products_subscr as $prod_subs ) {
        $products_arr[] = $prod_subs->ID;
    }

    // Testing if current product is a subscription product
    if (in_array( $product_id, $products_arr) ){

        // Declaring empties arrays
        $subscribers_arr = array(); // ALL subscribers IDS
        $active_subscriptions_arr = array(); // ALL actives subscriptions
        $active_subscription_products_arr = array(); // ALL actif subscription products IDS IDS
        $subscriber_subscriptions = array();

        // Getting arrays of "active" IDS for subscribers, subscriptions orders and subscription products
        $subscribers = get_users( array( 'role' => 'subscriber') );
        foreach( $subscribers as $subscriber ) {
            $subscriber_arr[] = $subscriber->ID;
            $subscriptions = wcs_get_users_subscriptions($subscriber->ID);
            foreach ($subscriptions as  $key => $subscription ){
                $subscription_status = $subscription->post->post_status;
                if ( $subscription_status == 'wc-active' ) { // active subscriptions only
                    $subscription_id = $subscription->post->ID;
                    $order_id = $subscription->order->post->ID; // order ID (corresponding to the subscription ID)
                    $active_subscriptions_arr[] = $subscription->post->ID;
                    $order_items = $subscription->order->get_items();
                    // Getting all the products in the Order
                    foreach ( $order_items as $item ) {
                        // $item_id = $item[product_id];

                        // Avoiding to add existing products in the array 
                        if( !in_array( $product_id, $active_subscription_products_arr ))
                            $active_subscription_products_arr[] = $item[product_id];
                    }
                }
            }
        }
    }
    if (in_array( $product_id, $active_subscription_products_arr ) ) return true;
    else return false;
}