PHP 實現可復用的購物車類（基於 MySQL + Session）

設計思路

使用資料庫持久化購物車數據，以 session_id 區分用戶，封裝增、刪、改、查、統計等操作，便於在多頁面復用。

資料表結構

-- 商品表
CREATE TABLE inventory (
    id INT(4) NOT NULL AUTO_INCREMENT PRIMARY KEY,
    product TINYTEXT NOT NULL,
    description TINYTEXT NOT NULL,
    price FLOAT(10,2) DEFAULT '0.00' NOT NULL,
    category CHAR(1) DEFAULT '' NOT NULL,
    KEY price (price)
);

-- 購物車表
CREATE TABLE shopping (
    id INT(4) NOT NULL AUTO_INCREMENT PRIMARY KEY,
    session TINYTEXT NOT NULL,
    product TINYTEXT NOT NULL,
    quantity TINYTEXT NOT NULL,
    KEY id (id)
);

核心類代碼

<?php
class Cart {
    // 檢查商品是否已在購物車
    function check_item($table, $session, $product) {
        $query = "SELECT * FROM $table WHERE session='$session' AND product='$product'";
        $result = mysql_query($query);
        if (!$result) return 0;
        $num = mysql_num_rows($result);
        if ($num == 0) return 0;
        $row = mysql_fetch_object($result);
        return $row->quantity;
    }

    // 添加/更新商品數量
    function add_item($table, $session, $product, $quantity) {
        $qty = $this->check_item($table, $session, $product);
        if ($qty == 0) {
            $query = "INSERT INTO $table (session, product, quantity) VALUES ('$session', '$product', '$quantity')";
        } else {
            $quantity += $qty;
            $query = "UPDATE $table SET quantity='$quantity' WHERE session='$session' AND product='$product'";
        }
        mysql_query($query);
    }

    // 刪除商品
    function delete_item($table, $session, $product) {
        $query = "DELETE FROM $table WHERE session='$session' AND product='$product'";
        mysql_query($query);
    }

    // 修改數量
    function modify_quantity($table, $session, $product, $quantity) {
        $query = "UPDATE $table SET quantity='$quantity' WHERE session='$session' AND product='$product'";
        mysql_query($query);
    }

    // 清空購物車
    function clear_cart($table, $session) {
        $query = "DELETE FROM $table WHERE session='$session'";
        mysql_query($query);
    }

    // 計算總價
    function cart_total($table, $session) {
        $query = "SELECT * FROM $table WHERE session='$session'";
        $result = mysql_query($query);
        $total = 0;
        while ($row = mysql_fetch_object($result)) {
            $q = "SELECT price FROM inventory WHERE product='$row->product'";
            $r = mysql_query($q);
            $p = mysql_fetch_object($r);
            $total += $p->price * $row->quantity;
        }
        return $total;
    }

    // 獲取購物車詳情（含商品信息）
    function display_contents($table, $session) {
        $query = "SELECT * FROM $table WHERE session='$session' ORDER BY id";
        $result = mysql_query($query);
        $contents = array(); $count = 0;
        while ($row = mysql_fetch_object($result)) {
            $q = "SELECT * FROM inventory WHERE product='$row->product'";
            $r = mysql_query($q);
            $inv = mysql_fetch_object($r);
            $contents['product'][$count] = $inv->product;
            $contents['price'][$count] = $inv->price;
            $contents['quantity'][$count] = $row->quantity;
            $contents['total'][$count] = $inv->price * $row->quantity;
            $contents['description'][$count] = $inv->description;
            $count++;
        }
        $contents['final'] = $this->cart_total($table, $session);
        return $contents;
    }

    // 獲取商品種類數
    function num_items($table, $session) {
        $query = "SELECT * FROM $table WHERE session='$session'";
        $result = mysql_query($query);
        return mysql_num_rows($result);
    }

    // 獲取商品總件數
    function quant_items($table, $session) {
        $query = "SELECT * FROM $table WHERE session='$session'";
        $result = mysql_query($query);
        $quant = 0;
        while ($row = mysql_fetch_object($result)) $quant += $row->quantity;
        return $quant;
    }
}
?>

使用示例

<?php
session_start();
if (!isset($_SESSION['scid'])) {
    $_SESSION['scid'] = md5(uniqid(rand()));
    setcookie('scid', $_SESSION['scid'], time()+14400); // 4 小時
}
include 'shoppingcart.php';
$cart = new Cart();
$link = mysql_connect('localhost', 'user', 'pass');
mysql_select_db('shop_db', $link);

// 添加商品
$cart->add_item('shopping', $_SESSION['scid'], 'P001', 2);

// 顯示購物車
$items = $cart->display_contents('shopping', $_SESSION['scid']);
foreach ($items['product'] as $i => $prod) {
    echo "$prod x {$items['quantity'][$i]} = {$items['total'][$i]}
";
}
echo "總計: {$items['final']}";
?>

安全性提醒

• 原代碼直接拼接 SQL，存在注入風險。實際項目請改用 mysqli/PDO 預處理語句。
• mysql_* 函數已棄用（PHP 7+ 移除），請遷移至 mysqli 或 PDO。
• Session ID 建議使用 PHP 內建 session_id()，無需自行生成 Cookie。