如何使用PHP编写库存管理系统中的商品入库功能代码

<form action="submit_inventory.php" method="post">
    <label for="productid">商品ID：</label>
    <input type="text" id="productid" name="productid"><br><br>
    <label for="productname">商品名称：</label>
    <input type="text" id="productname" name="productname"><br><br>
    <label for="productprice">商品价格：</label>
    <input type="text" id="productprice" name="productprice"><br><br>
    <label for="inventory">入库数量：</label>
    <input type="number" id="inventory" name="inventory"><br><br>
    <input type="submit" value="提交">
</form>

<?php

// 连接数据库
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "dbname";

$conn = new mysqli($servername, $username, $password, $dbname);
if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}

// 获取表单数据
$productid = $_POST['productid'];
$productname = $_POST['productname'];
$productprice = $_POST['productprice'];
$inventory = $_POST['inventory'];

// 验证数据
if (empty($productid) || empty($productname) || empty($productprice) || empty($inventory)) {
    echo "请填写完整信息";
} else {
    // 插入商品信息
    $sql_insert_product = "INSERT INTO product (productid, productname, productprice, inventory) VALUES ('$productid', '$productname', '$productprice', '$inventory')";
    if ($conn->query($sql_insert_product) === TRUE) {
        echo "商品插入成功";
    } else {
        echo "商品插入失败: " . $conn->error;
    }

    // 插入入库记录
    $sql_insert_inventory = "INSERT INTO inventory (productid, quantity, datetime) VALUES ('$productid', '$inventory', NOW())";
    if ($conn->query($sqL_insert_inventory) === TRUE) {
        echo "入库记录插入成功";
    } else {
        echo "入库记录插入失败: " . $conn->error;
    }
}

// 关闭数据库连接
$conn->close();

?>