AJAX request response

I'm new with AJAX. I'm sending a request to start a PHP code on another page where couple of things need to happen. I have an algorithm on that page checking if all the things were done properly in right order. What I need is to return that boolean back to AJAX file, so that it would know that request was not only received, but finished in an intended way, so that I can add a success: function that would give a OK/NEY experience to the user.

Solution

Your folder:

AnyFolderName
             |--- index.php
             |--- script.php

Index.php:

<!DOCTYPE html>
<html>
<head>
    <title>AJAX Request Sample</title>
    <script src="http://code.jquery.com/jquery-1.11.3.min.js"></script>
    <script type="text/javascript">
        function submitform(){
            //get value of input whos id is username
            var username = $('input#username').val();
            //data to post to script.php
            var post = {username: username};
            $.ajax({
                url: "script.php", //<-- PHP Script where you want to post your data
                type: "POST",
                data: post,
                success: function(data){
                    //callback when request is finished.
                    //in our script.php, we just echoed the posted username, so it alerts whatever username you have input.
                    alert(data);
                }
            });
        }
    </script>
</head>
<body>
    <form id="myForm">
         <input id="username" name="username">
    </form>
    <button onclick="submitform();"></button>
</body>
</html>

script.php:

<?php
     //print out the posted data you have passed from the AJAX request
     echo $_POST['username'];
?>