我在Woocommerce/Wordpress上工作，我是新来的，我想通过在其中添加使用过的优惠券来定制我的Woocommerce订单列表管理面板，但我在点击promo字段进行排序时遇到了一个小问题，它返回一个空结果。

在我的功能中。php

function sv_wc_cogs_add_order_promo_column_header($columns)
{

    $new_columns = array();

    foreach ($columns as $column_name => $column_info) {

        $new_columns[$column_name] = $column_info;

        if (\'order_total\' === $column_name) {
            $new_columns[\'order_promo\'] = __(\'Promo\', \'my-textdomain\');
        }
    }

    return $new_columns;
}

add_filter(\'manage_edit-shop_order_columns\', \'sv_wc_cogs_add_order_promo_column_header\', 20);



/**
 * Adds \'Profit\' column content to \'Orders\' page immediately after \'Total\' column.
 *
 * @param string[] $column name of column being displayed
 */
add_action( \'manage_shop_order_posts_custom_column\', \'sv_wc_cogs_add_order_promo_column_content\',20 ,4 );
function sv_wc_cogs_add_order_promo_column_content( $column, $post ) {
    global $post;

    if ( \'order_promo\' === $column ) {
        $order  = wc_get_order( $post->ID );
        $coupons = $order->get_used_coupons();

        foreach($coupons as $coupon){
            echo $coupon .\'<br>\';
        }
    }
}

add_filter( "manage_edit-shop_order_sortable_columns", \'custom_woo_admin_sort\' );
function custom_woo_admin_sort( $columns )
{
    $custom = array(
        \'order_promo\'    => \'_order_promo\',
    );
    $sortable_columns[ \'_order_promo\' ] = \'order_promo\';
    return wp_parse_args( $custom, $columns );
}


// Here is the problem cause the sort is not good ! It sort with strange value
add_action(\'pre_get_posts\', \'custom_promocode_orderby\');
function custom_promocode_orderby( $query ) {
    if ( !is_admin() ){ return; }

    $orderby = $query->get(\'orderby\');
    if (\'_order_promo\' == $orderby){
        $meta_query = array(
            \'relation\' => \'OR\',
            array(
                \'key\' => \'id\',
                \'compare\' => \'NOT EXISTS\',
            ),
            array(
                \'key\' => \'_order_promo\',
            ),
        );
      $query->set(\'order\',    \'ASC\' );
      $query->set(\'orderby\', $meta_query);
    }
}

抱歉，如果我的代码不是一个好的做法！我是wordpress的noob。。。