1.问题：woocommerce4.1.0:\woocommerce\templates\myaccount dashboard.php
在第46行中，我想添加包含一些sql查询的代码，以向活动客户显示他帐户上有多少钱（“ $account_balance ）在“我的帐户”下。
我可以获取活动用户\u id:

$user_id = get_current_user_id();
$user = new WC_Customer( $user_id );

但我不知道如何得到电流 customer_id （由于表中不包含 user_id ).
2.我试过的：
我在phpmyadmin中创建了一个名为 L16_transfers 包含以下列：

transaction_id
customer_id
transfer_date
eur_transferred
eur_refunded
first_name
last_name
order_id

从这个自定义表中，我想获得所有入站和出站事务( eur_transferred 以及 eur_refunded ).
我用的另一张table是 L16_wc_order_stats 我想从中得到 net_total . 然而， L16_wc_order_stats 包含列 customer_id 但不是 user_id （数据库中分配的编号不同）。
3个sql查询应该返回-转账-退款-订单的总和，我将加/减这些总和以得到当前的总余额。
3.我的代码：

<?php

//
// variable declarations
//

global $account_balance, $transferred_total, $refunded_total, $orders_total, $net_total;
global $wpdb;

$account_balance = 0.00;
$transferred_total = 0.00;
$refunded_total = 0.00;
$orders_total = 0.00;

$user_id = get_current_user_id();
$user = new WC_Customer( $user_id );

$customer_id = get_customer_id();
$customer = new WC_Customer( $customer_id );

//
// first output testing
//

echo "Customer id: " . print_r($customer_id). "<br>"; // I always get NULL, also tried with sprintf and echo
echo "Customer id: " . $customer_id . "<br>";
print_r($customer_id);
sprintf($customer_id);

print_r ($customer); // I always get NULL, also tried with sprintf and echo
echo "Customer: " . $customer. "<br><br>";
echo "Customer: " . print_r($customer);

echo "User id: " . $user_id . "<br>"; // user_id output works
var_dump($user["id"]["display_name"]["role"]);
echo var_dump($user['id']);

//
// Three SQL queries
//

$transferred_total = $wpdb->get_var("

    SELECT SUM(eur_transferred) FROM L16_transfers WHERE customer_id = $customer_id
");

echo "<b>" . "Transfers grand total: " . "</b>" . $transferred_total . " €<br>";

$refunded_total = $wpdb->get_var("

    SELECT SUM(eur_refunded) FROM L16_transfers WHERE customer_id = $customer_id
");

echo "<b>" . "Refunds grand total: " . '</b>' . $refunded_total . " €<br>";

$orders_total = $wpdb->get_var("

    SELECT SUM(net_total) FROM L16_wc_order_stats WHERE customer_id = $customer_id
");

echo "<b>Orders grand total: </b>" . $orders_total . " €<br><br>";
var_dump ($orders_total); // solely for testing output

$account_balance = $transferred_total + $refunded_total - $orders_total

var_dump ($account_balance);
echo $account_balance;
echo "<h1>Your current account balance: </h1><b>" . $account_balance . "</b>";

?>
</p>

我认为我在处理数组或错误解释查询输出方面犯了一些错误。
（我是woocommerce/wordpress的新手，只掌握php和sql的基本知识。）
非常感谢您在更正我的代码时提供的任何帮助。