You are not sending the URL anywhere at the moment.
You should use curl to post this URL with any variables you need. However, you are also trying to post a full order which will not work at all.
I am not sure what your API/system requires from your website but if you want to send only the order ID then this should look something like this:
add_action( 'woocommerce_payment_complete', 'my_api_call');
function my_api_call( $order_id ){
// Order Setup Via WooCommerce
$order = new WC_Order( $order_id );
// Iterate Through Items
$items = $order->get_items();
$url = "http://example.com/Api/WooCommerceApi/SaveSubscriptionAndZoomData";
$orderid = "OrderId=".$order_id;
$ch = curl_init( $url );
curl_setopt( $ch, CURLOPT_POST, 1);
curl_setopt( $ch, CURLOPT_POSTFIELDS, $orderid);
curl_setopt( $ch, CURLOPT_FOLLOWLOCATION, 1);
curl_setopt( $ch, CURLOPT_HEADER, 0);
curl_setopt( $ch, CURLOPT_RETURNTRANSFER, 1);
$response = curl_exec( $ch );
}
The $response
should give you a message. Important: this code is untested but you should be able to get the solution from here.
Source: POST data to a URL in PHP