title: form sends values that are not changing anything
body: <p>I have a simple form:</p>
  
  <pre><code>&lt;form id="change_id" action="change.php?change=profile"
        method="POST" enctype="multipart/form-data"&gt;
      &lt;input id="change_username" required name="jmeno_new"
             type="text" placeholder="New Username"&gt;
  &lt;/form&gt;
  </code></pre>
  
  <p>Also, I am sending data from my <code>form</code> element via AJAX request like so:</p>
  
  <pre><code>save_button.addEventListener('click', function ()
  {
      var fd = new FormData(change_id);
      XXHR().request(change_id.getAttribute("action"), function(r){
          var obj = JSON.parse(r);
          if (obj.type == 'success')
          {}
  
          else if (obj.type == 'success_un')
          {
              console.log("YEAH! THAT WORKS.");
          }
      }, function(){}, true, fd);
  }, false);
  </code></pre>
  
  <p>And I get it with my PHP file like so:</p>
  
  <pre><code>$new_un = $_POST['jmeno_new'];
  $sql_update = ("UPDATE myTable SET `name`='$new_un' WHERE `name`='$name'");
  $out = array('type' =&gt; 'success_un');
  exit(json_encode($out));
  </code></pre>
  
  <p>So if the data is set, I can only see that AJAX request was successful, but it does not change anything in my database.</p>
  
  <p><strong>What it should do?</strong></p>
  
  <p>It should update <code>myTable</code> where it should replace the old name with the new one, got via <code>$_POST</code>.</p>
  
  <p>This does not work.. how? Why?</p>