Print orders in chronological order in Picklist-PDF Invoice/Packing Slip for WooCommerce

functions.php

<?php

add_filter('wf_pklist_alter_package_grouped_order_items','wt_pklist_sort_items_asc_in_picklist',10,5);
function wt_pklist_sort_items_asc_in_picklist($item_arr, $grouping_config, $order_package, $template_type, $order)
{
    if($template_type=='picklist')
    {
        $id_arr=array();
        foreach ($item_arr as $id => $item)
        {   
            $id_arr[]=$id;
        }
        array_multisort($id_arr, SORT_DESC, $item_arr);
    }
    return $item_arr;
}