警报中的Ajax响应

Question

I have a test.php file as:

<?php
    header('Content-type: application/json');
    $json_array = array();
    $json_array['success']='1';
    echo json_encode($json_array);
?>

On an input button click response needed in an alert.

 <input type="button" id="btnSubmit" value="AJAX Request" />