XMLHttpRequest not getting response after inserting in MySQL using PHP - php

Question

I have surfed a lot and i have also tried all the possibilities to get this done, but still it is not working. What I am doing is, trying to insert product category using XMLHttpRequest and if recorded inserted successfully it should return true as response else false as response.
front page:
<form id="form_validation" method="POST" onsubmit="InsertCategory()">
<div class="form-group form-float">
<div class="form-line">
<input type="text" class="form-control" name="category_name" id="category_name" required>
<label class="form-label">Category Name</label>
</div>
</div>
<button class="btn btn-primary waves-effect" type="submit" name="submit">SUBMIT</button>
</form>
<script>
function InsertCategory()
{
var category_name=document.getElementById("category_name").value;
var operation="insert";
var url = "includes/ajax/category_master/categoryOperations.php";
//var url = "includes/ajax/getDocuments.php";
var params = "category_name="+category_name+"&operation="+operation;
var http = new XMLHttpRequest();
http.onreadystatechange = function()
{
console.log("rs "+http.response);
console.log(http.readyState);
console.log(http.status);
if(http.readyState == 4 && http.status == 200)
{
}
}
http.open("POST", url, true);
http.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
http.send(params);
}
</script>
here is categoryOperations page
<?php include_once("connection.php");
$operation=$_POST["operation"];
switch($operation)
{
case "insert":
$category_name=$_POST["category_name"];
$query="insert into product_category(category_name)values(:category_name)";
$stmt=$con->prepare($query);
$stmt->bindParam(":category_name",$category_name);
if($stmt->execute())
{
echo "true";
}
else
{
echo "false";
}
break;
case "update":
break;
case "delete":
break;
}
?>
What happens here is, all code work fine, category inserts in product_category table but i am not able to receive true as response.
if I comment $stmt->execute() in categoryOperations page and echo true then it works fine, on console I get true. but if query is executed it does not return anything.
I am not able to understand this behavior of the code.

Answer 1

Got Solution
The problem was, i have written
<form id="form_validation" method="POST" onsubmit="InsertCategory()">
that was sending two request. with form as well as from xmlhttprequest.
i just removed <form> tag and called InsertCateory() on submit button
<button class="btn btn-primary waves-effect" type="submit" onClick="InsertCategory()" name="submit">SUBMIT</button>