leaky-paywall-add-fee.php

<?php

add_action('leaky_paywall_after_create_recurring_customer', 'zeen101_add_fee_to_recurring_checkout');

function zeen101_add_fee_to_recurring_checkout( $customer ) {

    $fee_amount = 999; // in cents

    $stripe = leaky_paywall_initialize_stripe_api();

    try {
            $invoice_item = $stripe->invoiceItems->create([
                'amount' => $fee_amount,
                'currency' => leaky_paywall_get_currency(),
                'customer' => $customer->id,
                'description' => 'Sign up fee',
            ]);

            $invoice = $stripe->invoices->create([
                'customer' => $customer->id,
                'auto_advance' => true, /* auto-finalize this draft after ~1 hour */
            ]);

        } catch (\Throwable $th) {
            leaky_paywall_log($customer, 'leaky paywall - error creating invoice');
            wp_send_json(array(
                'error'  => $th->jsonBody
            ));
        }
}