在向数组添加键之前检查变量是否已设置 - PHP

Question

I'm using the Stripe API like so:

$coupon = $_POST["coupon"];

$subscription = \Stripe\Subscription::create(array(
  "customer" => $customer->id,
  "plan" => $plan,
  "coupon" => $coupon,
));

This works great when $coupon is set and it's a valid coupon code. If I leave it blank (i.e., customer didn't include a coupon code in form submitted), Stripe throws an error. If I include a coupon code that doesn't exist in Stripe, it throws an error.

So, the question is, how do I build this array to NOT have the coupon key when the variable $coupon is empty?

Answer 1

$payment_data = array(
  "customer" => $customer->id,
  "plan" => $plan,
);
if (!empty($_POST['coupon'])) {
    $payment_data["coupon"] = $_POST['coupon'];
}

$subscription = \Stripe\Subscription::create($payment_data);