訂單結算submit_order.php（扣庫存,扣帳號金額）

<?php
    header("Content-type: text/html; charset=utf-8");
    session_start();
    include_once("DB.class.php");

    //測試數據,初始化金額爲1000.
    // $_SESSION['account'] = 1000;


    // 得到訂單總額
    $order_money = $_GET['total'];

    //得到帳戶餘額
    $uid = $_SESSION['uid'];
    // var_dump($uid);
    $sql = "select account from tb_user where id = $uid";
    $account = $dao->getOne($sql);

    if($account>=$order_money){
        $order = $_SESSION['order'] ;
        // 從數據庫中減掉庫存
        
        foreach($order as $item){
            $kucun = $item['num'];
            $id = $item['goods_id'];
            $sql = "update tb_goods set number =number-{$kucun} where id ={$id}";
            // var_dump($sql);
            // die();
            $dao->exec($sql);
        }
        
        
            //減去金額    
        $account-=$order_money;
        $sql = "update tb_user set account = {$account} where id = $uid";
        $dao->exec($sql);
        echo "下單成功！帳戶餘額：￥$account";
        $_SESSION['order'] = '';
    }else{
        echo "下單失敗！訂單所需金額:$order_money,帳戶餘額：￥$account,餘額不足!!";
        
    }
    
    
?>

業務邏輯

下單以後用戶要進行判斷庫存，和用戶金額是否充足。

充足的話進行修改數據庫的庫存和餘額。