I want to Update my database with a variable from javascript.

This is my javascript code i want the testusersGeld variable to transfare over to php.

var testusersGeld = 111;

var sendUsersGeld = new XMLHttpRequest();

sendUsersGeld.open("POST", "usersGeldSenden.inc.php");
sendUsersGeld.setRequestHeader("Content-Type", "application/json");
sendUsersGeld.send(testusersGeld);

and this is my php code:

<?php

session_start();

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

$object = json_decode($requestPayload);

var_dump($object);

if(isset($_POST['update']))
{

    require_once 'includes\dbh.inc.php';

    $query = "UPDATE users SET usersGeld='".$object."' WHERE usersName LIKE '{$_SESSION["usersName"]}'";
    
    $result = mysqli_query($conn, $query );

    if($result)
    {   
        echo 'Data Updated';
    }else{
        echo 'Data Not Updated';
    }
    mysqli_close($conn);
}

When i var_dump than i can see the 111 but when i try to echo it out it wont work. The part of Update works when i use another variable.