Javascript 使用xmlHttpRequest接收响应文本，请求i'；我不确定

我使用这段代码使用ajax向数据库添加数据。以下是html：

<form>
          Product Name:</br>
          <input type=text name=productName id="addProductName"></br>
          Product Description:</br>
          <input type=text name=productDescription id="addProductDescription"></br>
          Product Quantity:</br>
          <input type=number name=productQuantity id="addProductQuantity"></br>
          <button id="addProduct" type=button>Add Product</button>
        </form>
        <div id="productAdded">test</div>
        <script language="JavaScript" type="text/javascript" src="../javascript/test.js"></script>

以下是php：

<?php
$servername = "localhost";
$username = "root";
$password = "";
$dbname = "products";

try {
  $conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
  $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

  $productName = $_GET['a'];
  $productDescription = $_GET['b'];
  $productQuantity = $_GET['c'];
  $sql = "INSERT INTO Product (ProductName, ProductDescription, ProductQuantity) VALUES ('$productName','$productDescription','$productQuantity')";
  $conn->exec($sql);
  echo 'Product ' . $productName . ' with quantity: ' . $productQuantity . ' Added';
}
catch(PDOException $e)
{
  echo $sql . "<br>" . $e->getMessage();
}

$conn = null;

---

执行
getElementById
时，将返回
HTMLInputElement
。之后，需要获取此元素的值：

var productName = document.getElementById("addProductName").value;
var productDescription = document.getElementById("addProductDescription").value;
var productQuantity = document.getElementById("addProductQuantity").value;

您实际上并没有从输入字段中获取值，请使用value属性获取它

var productName = document.getElementById("addProductName").value;
var productDescription = document.getElementById("addProductDescription").value;
var productQuantity = document.getElementById("addProductQuantity").value;

此外，您还应该对日期进行编码，以防其中有任何特殊字符

var url = "insert.php?a=" + encodeURIComponent(productName) + "&b=" + encodeURIComponent(productDescription) + "&c=" + encodeURIComponent(productQuantity);

var url = "insert.php?a=" + encodeURIComponent(productName) + "&b=" + encodeURIComponent(productDescription) + "&c=" + encodeURIComponent(productQuantity);