Javascript 无法在PHP内回显ajax中发送的POST参数

我将send方法中的两个参数发送到index.php。但是PHP返回一个错误“未定义索引”。echo$_POST['fname']

---

为了通过Ajax发送表单数据，必须指定请求的内容类型。在您的情况下，它将是

'application/x-www-form-urlencoded

：

xhr.setRequestHeader('Content-Type','application/x-www-form-urlencoded');

因此，您的代码将是：

submit.addEventListener("click", function(e){
  e.preventDefault(); 
  var xhr = new XMLHttpRequest();
  xhr.open("POST", "index.php", true);
  xhr.setRequestHeader("X-Requested-With", "XMLHttpRequest");
  xhr.setRequestHeader('Content-Type','application/x-www-form-urlencoded');
  xhr.onreadystatechange = function () {
    if(xhr.readyState == 4 && xhr.status == 200) {
      var result = xhr.responseText;
      console.log(result);
    }
  }
  xhr.send("fname=Henry&lname=Ford");
});

submit.addEventListener("click", function(e){
  e.preventDefault(); 
  var xhr = new XMLHttpRequest();
  xhr.open("POST", "index.php", true);
  xhr.setRequestHeader("X-Requested-With", "XMLHttpRequest");
  xhr.setRequestHeader('Content-Type','application/x-www-form-urlencoded');
  xhr.onreadystatechange = function () {
    if(xhr.readyState == 4 && xhr.status == 200) {
      var result = xhr.responseText;
      console.log(result);
    }
  }
  xhr.send("fname=Henry&lname=Ford");
});