如何使用PHP编写库存管理系统的基础框架代码

<?php
class InventoryManagement {
    private $db;

    public function __construct($host, $username, $password, $database) {
        $this->db = new mysqli($host, $username, $password, $database);

        if ($this->db->connect_error) {
            die("连接数据库失败：" . $this->db->connect_error);
        }
    }

    public function getProductStock($product_id) {
        $query = "SELECT product_stock FROM products WHERE product_id = ?";
        $stmt = $this->db->prepare($query);
        $stmt->bind_param("s", $product_id);
        $stmt->execute();
        $stmt->bind_result($product_stock);
        $stmt->fetch();
        $stmt->close();

        return $product_stock;
    }

    public function addProductStock($product_id, $quantity) {
        $current_stock = $this->getProductStock($product_id);
        $new_stock = $current_stock + $quantity;
        $query = "UPDATE products SET product_stock = ? WHERE product_id = ?";
        $stmt = $this->db->prepare($query);
        $stmt->bind_param("is", $new_stock, $product_id);
        $stmt->execute();
        $stmt->close();

        $this->logAction("Add Product Stock - Product ID: $product_id, Quantity: $quantity");
    }

    public function reduceProductStock($product_id, $quantity) {
        $current_stock = $this->getProductStock($product_id);

        if ($current_stock < $quantity) {
            die("库存不足");
        }

        $new_stock = $current_stock - $quantity;
        $query = "UPDATE products SET product_stock = ? WHERE product_id = ?";
        $stmt = $this->db->prepare($query);
        $stmt->bind_param("is", $new_stock, $product_id);
        $stmt->execute();
        $stmt->close();

        $this->logAction("Reduce Product Stock - Product ID: $product_id, Quantity: $quantity");
    }

    public function logAction($action) {
        $query = "INSERT INTO log (log_type, log_time) VALUES (?, NOW())";
        $stmt = $this->db->prepare($query);
        $stmt->bind_param("s", $action);
        $stmt->execute();
        $stmt->close();
    }
}
?>

<?php
// 创建库存管理对象
$inventory = new InventoryManagement("localhost", "root", "password", "inventory_management");

// 添加产品库存
$inventory->addProductStock("P001", 10);

// 减少产品库存
$inventory->reduceProductStock("P001", 5);

// 获取产品库存
$product_stock = $inventory->getProductStock("P001");
echo "Product Stock: $product_stock";
?>