How to send user data in json format to another server when user register on wordpress site in PHP

Sending and receiving data in JSON format using POST method

xhr = new XMLHttpRequest();
var url = "url";
xhr.open("POST", url, true);
xhr.setRequestHeader("Content-type", "application/json");
xhr.onreadystatechange = function () { 
    if (xhr.readyState == 4 && xhr.status == 200) {
        var json = JSON.parse(xhr.responseText);
        console.log(json.email + ", " + json.password)
    }
}
var data = JSON.stringify({"email":"[email protected]","password":"101010"});
xhr.send(data);

Sending a receiving data in JSON format using GET method

xhr = new XMLHttpRequest();
var url = "url?data=" + encodeURIComponent(JSON.stringify({"email":"[email protected]","password":"101010"}));
xhr.open("GET", url, true);
xhr.setRequestHeader("Content-type", "application/json");
xhr.onreadystatechange = function () { 
    if (xhr.readyState == 4 && xhr.status == 200) {
        var json = JSON.parse(xhr.responseText);
        console.log(json.email + ", " + json.password)
    }
}
xhr.send();

Handling data in JSON format on the server-side using PHP

// Handling data in JSON format on the server-side using PHP
header("Content-Type: application/json");
// build a PHP variable from JSON sent using POST method
$v = json_decode(stripslashes(file_get_contents("php://input")));
// build a PHP variable from JSON sent using GET method
$v = json_decode(stripslashes($_GET["data"]));
// encode the PHP variable to JSON and send it back on client-side
echo json_encode($v);