无法在ajax请求中获取php中的$ _POST值

Question

Here is my index.html

<script>
    var xml = new XMLHttpRequest();
    xml.onreadystatechange = function(){
        if (xml.readyState === 4 && xml.status === 200) {
            console.log(xml.responseText);
        }
    }
    xml.open("POST", "ajax.php", true);
    var data = new FormData();
    data.append("name","Sahan");
    xml.send(data);
</script>

And here is my ajax.php

<?php
echo "Hello " . $_POST["name"];
?>

When I run this on my localhost result is

: Undefined index: name in on line
Hello

But when I am using It is Working Correctly...

And my question is how I send ajax using JavaScript without JQuery..?

Answer 1

You have to pass proper header information along with request when you use ajax with post data

<script>
    var xml = new XMLHttpRequest();
    xml.onreadystatechange = function(){
        if (xml.readyState === 4 && xml.status === 200) {
            console.log(xml.responseText);
        }
    }
    xml.open("POST", "ajax.php", true);
    //Send the proper header information along with the request
    xml.setRequestHeader("Content-type", "application/x-www-form-urlencoded");

    /*var data = new FormData();
    data.append("name","Stackoverflow");*/
    xml.send("name=Stackoverflow");
</script>

Answer 2

You can use this code in your javascript function.

var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function() {
    if (this.readyState == 4 && this.status == 200) {
      document.getElementById("demo").innerHTML = this.responseText;
    }
  };
xhttp.open("POST", "ajax_test.php", true);
xhttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
xhttp.send("fname=Stack&lname=Overflow");

for more details Ajax at w3schools