如何使用Stripe和PHP（用于订阅）增加付款次数

Question

我正在尝试设置订阅并计算付款次数（使用Webhook）。我正在使用此文档：https://stripe.com/docs/recipes/installment-plan#signing-up-a-customer-for-an-installment-plan

但是它是Ruby on Rails。我试图添加元数据来计算付款：

       $subscription = \Stripe\Subscription::create(array(
  "customer" => $customer->id,
  "items" => array(
      array(
          "plan" => $plan->id,
      ),
  ),   
   "metadata" => ["number_payments" => 0]));

然后在我的webhook页面中，我想检索订阅并增加付款次数，但是我不了解并且不知道如何使用php（来自此处的Stripe示例代码）：

def increment_payments_count(event)
# Grab the subscription line item.
sub =  event.data.object.lines.data[0]

# Execute only for installment plans.
if !sub.metadata[:installments_paid].nil?
# Recommendation: Log invoices and check for duplicate events.
# Recommendation: Note that we send $0 invoices for trials.
#                 You can verify the `amount_paid` attribute of
#                 the invoice object before incrementing the count.

    # Retrieve and increment the number of payments.
    count = sub.metadata[:installments_paid].to_i
    count += 1

谢谢您的帮助！