帮我用PHP写一个进销存后端管理系统。前端使用Java语言来写

好的，首先你需要安装一个PHP开发环境，比如XAMPP或者WAMP。

然后你可以开始编写PHP代码来实现进销存后端管理系统。以下是一个简单的示例代码：

<?php
// 连接数据库
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

$conn = mysqli_connect($servername, $username, $password, $dbname);

// 检查连接
if (!$conn) {
    die("Connection failed: " . mysqli_connect_error());
}

// 处理请求
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    $action = $_POST["action"];
    switch ($action) {
        case "add_product":
            // 添加商品
            $name = $_POST["name"];
            $price = $_POST["price"];
            $quantity = $_POST["quantity"];
            $sql = "INSERT INTO products (name, price, quantity) VALUES ('$name', '$price', '$quantity')";
            if (mysqli_query($conn, $sql)) {
                echo "Product added successfully";
            } else {
                echo "Error: " . $sql . "<br>" . mysqli_error($conn);
            }
            break;
        case "update_product":
            // 更新商品信息
            $id = $_POST["id"];
            $name = $_POST["name"];
            $price = $_POST["price"];
            $quantity = $_POST["quantity"];
            $sql = "UPDATE products SET name='$name', price='$price', quantity='$quantity' WHERE id='$id'";
            if (mysqli_query($conn, $sql)) {
                echo "Product updated successfully";
            } else {
                echo "Error: " . $sql . "<br>" . mysqli_error($conn);
            }
            break;
        case "delete_product":
            // 删除商品
            $id = $_POST["id"];
            $sql = "DELETE FROM products WHERE id='$id'";
            if (mysqli_query($conn, $sql)) {
                echo "Product deleted successfully";
            } else {
                echo "Error: " . $sql . "<br>" . mysqli_error($conn);
            }
            break;
    }
}

// 查询商品列表
$sql = "SELECT * FROM products";
$result = mysqli_query($conn, $sql);

if (mysqli_num_rows($result) > 0) {
    // 输出数据
    while($row = mysqli_fetch_assoc($result)) {
        echo "id: " . $row["id"]. " - Name: " . $row["name"]. " - Price: " . $row["price"]. " - Quantity: " . $row["quantity"]. "<br>";
    }
} else {
    echo "No products found";
}

// 关闭连接
mysqli_close($conn);
?>

这个示例代码实现了添加、更新和删除商品的功能，并且查询并输出了所有商品的信息。你可以根据你的具体需求来修改代码。关于前端使用Java语言来写，你可以使用Java Swing或者JavaFX来实现。