WooCommerce - Google Review Opt-In

<?php
  // WooCommerce - Google Review Opt-In
  add_action( 'woocommerce_thankyou', 'google_review_opt_in' );
  function google_review_opt_in( $order_id ) {
    $order = wc_get_order( $order_id );
    $datetime_object = $order->get_date_created();
    $datetime_object->modify( '+21 day' );
    $delivery_date = $datetime_object->date( 'Y-m-d' );
    ?>
<script>
  // Google Review Opt-In
  window.renderOptIn = function() {
    window.gapi.load('surveyoptin', function() {
      window.gapi.surveyoptin.render(
        {
          "merchant_id": 9085387,
          "order_id": "<?php echo $order->get_id(); ?>",
          "email": "<?php echo $order->get_billing_email(); ?>",
          "delivery_country": "<?php echo $order->get_billing_country(); ?>",
          "estimated_delivery_date": "<?php echo $delivery_date; ?>",
         });
    });
  }
</script>
   <?php
  } // end function