Php 将空记录发送到mysql

我正在尝试将数据从我的ionic应用程序发送到mysql。问题是当我点击submit按钮时，它实际上会在数据库中发布空记录

我的HTML代码

<form >
  <label class="item item-input">
    <span class="input-label">Product Name:</span>
    <input type="text" ng-model="productname">
  </label>
  <label class="item item-input">
    <span class="input-label">Product Price:</span>
    <input type="number" ng-model="productprice" >
  </label>
  <label class="item item-input">
    <span class="input-label" >Description:</span>
    <input type="text" ng-model="productdescription">
  </label>
  <input type="button" value="Submit" class="button button-assertive button-block" ng-click="submit()">
</form> 

这是我的PHP代码，用于将数据发布到数据库

<?php  

    header("Access-Control-Allow-Origin: *");
    header("Content-Type: application/json; charset=UTF-8");

    $conn = new mysqli("localhost", "root", "", "ionic");

    if ($conn->connect_error) {
        die("Connection failed: " .$conn->connect_error);
    } 

    $postdata = file_get_contents("php://input");

    if(isset($postdata) && !empty($postdata))
    {
    $request = json_decode($postdata);


    $pname = $request->productname;
    $pprice = $request->productprice;
    $pdescription = $request->productdescription;


     $sql = ("INSERT INTO `users` ( product_name, product_price, description) VALUES ('$pname', '$pprice', '$pdescription')");

      mysqli_query($conn, $sql);
  }

---

注意此处缺少的任何内容
'$http'，'$state，funct
？表示了解的语句。即使是这样也不安全！您是否在api.php上进行了var_转储（$request）？它的内容是什么？
<?php  

    header("Access-Control-Allow-Origin: *");
    header("Content-Type: application/json; charset=UTF-8");

    $conn = new mysqli("localhost", "root", "", "ionic");

    if ($conn->connect_error) {
        die("Connection failed: " .$conn->connect_error);
    } 

    $postdata = file_get_contents("php://input");

    if(isset($postdata) && !empty($postdata))
    {
    $request = json_decode($postdata);


    $pname = $request->productname;
    $pprice = $request->productprice;
    $pdescription = $request->productdescription;


     $sql = ("INSERT INTO `users` ( product_name, product_price, description) VALUES ('$pname', '$pprice', '$pdescription')");

      mysqli_query($conn, $sql);
  }