How can I append an empty array to FormData object?

Question

I have the following problem:

An html form that has N checkbox's used on a FormData to send a request through ajax with its information. On PHP, the $_POST['teste'] variable does not exists...

<form id="teste_form">
    <input type="checkbox" name="teste[]">
    <input type="checkbox" name="teste[]">
    <input type="checkbox" name="teste[]">
    <input type="checkbox" name="teste[]">...
</form>

<script>
    var form_data_obj = new FormData( document.getElementById('teste_form') );
    $.ajax({
        ...
        data: form_data_obj
        ...
    });
</script>

I know that I could use a "if(isset(...))" on PHP, but I really don't like that solution. To me, the best solution would be to send an empty array to PHP from the FormData object.

Obs: I tried somethings like, for example:

• form_data_obj.append('teste[]', undefined).
• form_data_obj.append('teste[]', 0).

But without success... The result on PHP is respectively: ["undefined"], ["0"]

I wanted to get $ _POST ['test'] = [] in PHP

Is that possible?

Answer 1

Smells like this: How to Submit empty array from HTML Form Post to PHP

Workaround: You can use a hidden input element with an empty value on client side, and an empty value check on the server side. With something like this:

var appended = null;
$('.confirm_appointment').submit(function(e) {

  if (appended !== null) appended.remove();
  /************************************/
  if ($("input[name='teste[]']:checked").length == 0) {
    appended = $("<input type='hidden' name='teste[]' value=''>").appendTo($(this));
  }
  /************************************/

  e.preventDefault();
  $(this).append(decodeURIComponent($(this).serialize()) + '<br />');
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<form name='confirm_appointment' method='post' class='confirm_appointment'>
  <input type='checkbox' name="teste[]" value='hello1' />
  <input type='checkbox' name="teste[]" value='hello2' />
  <input type='checkbox' name="teste[]" value='hello3' />
  <input type='checkbox' name="teste[]" value='hello4' />
  <input type='submit' class='update_appointment_button' value='submit' /><br />
</form>

And on PHP side:

$teste = array_filter($_POST["teste"]);