Woocommerce: change user role after completing order

🙂

I’m using wordpress with woocommerce, and I would like to automate the following step. When an order is completed, I would like to change the user role associated with that order id from ‘customer’ to ‘subscriber’.

By searching around, I think I should be able to accomplish this by using a hook in functions.php:

add_action( 'woocommerce_order_status_completed', 'change_role_from_customer_to_subscriber' );

Then add the function:

function change_role_from_customer_to_subscriber($order_id){
// code to change role to subscriber
}

In the code, I think I need to do 2 things:
1) get the user id that is associated with that order id
2) change role of that user id to subscriber

I’ve tried a lot, but I couldn’t get it to work (neither getting the right user id, nor changing the role of a user id). So any help would be appreciated! I’ve seen 2 related questions asked before on stack overflow, but unfortunately the answers there did not work for me. I hope someone can help me out!

Thanks a lot! 🙂

Edit:
Someone helped me out with the second part of the problem, so that’s great news for me 🙂

Unfortunately, I still haven’t figured out the first part: how to get the user id that is associated with the order id.
Any ideas?

Looking through the code there is a very relevant example:

function woocommerce_paying_customer( $order_id ) {

    $order = new WC_Order( $order_id );

    if ( $order->user_id > 0 ) {

        $old_spent = absint( get_user_meta( $order->user_id, '_money_spent', true ) );
        update_user_meta( $order->user_id, '_money_spent', $old_spent + $order->order_total );

        $old_count = absint( get_user_meta( $order->user_id, '_order_count', true ) );
        update_user_meta( $order->user_id, '_order_count', $old_count + 1 );
    }
}
add_action( 'woocommerce_order_status_completed', 'woocommerce_paying_customer' );

which reminds us that the $order_is passed to the woocommerce_order_status_completed hook. From the $order_id, you can create a new order object, with the user_id as a property.

Armed with that knowledge, I think we can just fix the inner guts of the function get a new user object from that user ID, and remove the old role and finally apply the new role.

function wpa_120656_convert_paying_customer( $order_id ) {

    $order = new WC_Order( $order_id );

    if ( $order->user_id > 0 ) {
        update_user_meta( $order->user_id, 'paying_customer', 1 );
        $user = new WP_User( $order->user_id );

        // Remove role
        $user->remove_role( 'customer' ); 

        // Add role
        $user->add_role( 'subscriber' );
    }
}
add_action( 'woocommerce_order_status_completed', 'wpa_120656_convert_paying_customer' );