EDD Recurring Payments - Set active currency during renewals

/**
 * Intercepts renewal payments in Easy Digital Downloads, setting the active currency to the one used
 * for the original subscription.
 *
 * HOW TO USE THIS CODE
 * Add the code to the bottom of your theme's functions.php file, and it
 * will run automatically. For more information: https://www.skyverge.com/blog/add-custom-code-to-wordpress/
 *
 * GPL DISCLAIMER
 * Because this code program is free of charge, there is no warranty for it, to the extent permitted by applicable law.
 * Except when otherwise stated in writing the copyright holders and/or other parties provide the program "as is"
 * without warranty of any kind, either expressed or implied, including, but not limited to, the implied warranties of
 * merchantability and fitness for a particular purpose. The entire risk as to the quality and performance of the program
 * is with you. should the program prove defective, you assume the cost of all necessary servicing, repair or correction.
 *
 * Need a consultation, or assistance to customise this code? Find us on Codeable: https://aelia.co/hire_us
 */
add_action('edd_recurring_process_add_renewal_payment', function() {
  if(empty($_POST['sub_id'])) {
    return;
  }
  // Load the subscription
  $subscription = new EDD_Subscription(absint($_POST['sub_id']));
  // Load the payment associated to the subscription
  $subscription_payment = new EDD_Payment($subscription->parent_payment_id);

  if(is_objext($subscription_payment)) {
    return;
  }

  // Fetch the currency from the original subscription payment
  $subscription_payment_currency = $subscription_payment->currency;
  // Set the active currency to the one from the subscription
  add_filter('edd_aelia_cs_selected_currency', function($selected_currency) use ($subscription_payment_currency) {
    return $subscription_payment_currency;
  }, 20);
}, 0);