// Add to cart after Gravity Form Submission
add_filter('gform_confirmation', 'custom_add_cart', 10, 4);
function custom_add_cart($confirmation, $form, $entry, $ajax) {
    if ($form['id'] == 285) { // Replace 285 with your form id
        $field_id = 1; // Replace with the ID of the checkbox items field
        $field = GFAPI::get_field($entry['form_id'], $field_id);

        $selected_items = array();
        if ($field instanceof GF_Field_Checkbox) {
            $selected_items = $field->get_value_export($entry, $field_id, false);
            $selected_items = explode(",", $selected_items);
        }

        $demo_id = rgar($entry, '3'); // Replace 3 with field id of demo id

        $items = array();
        if (!empty($selected_items)) {
            foreach ($selected_items as $selected_item) {
                $items[] = $selected_item;
                $items[] = '1'; // 1 is the quantity
            }
        }

        if (!empty($items)) {
            // Create the redirect URL
            $redirect_url = 'https://www.stampinup.com/cart?items=' . urlencode(implode(",", $items)) . '&demoid=' . urlencode($demo_id);

            // Set the confirmation type to redirect
            $confirmation = array('redirect' => $redirect_url);
        }
    }

    return $confirmation;
}