[Vuejs]-PHP sends back empty body

The empty response is returned for multiple reasons. See them explained below.

jQuery selector

It appears that the selector for finding the form uses the jQuery id selector:

this.$http.post('addalbum.php', new FormData($('#submitalbum')))

But the jQuery function (i.e. $()) returns a collection (an array):

var submitAlbumCollection = $('#submitalbum');
console.log('submitAlbumCollection: ', submitAlbumCollection);

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<form class="col s12" id="submitalbum" method="post" action="addalbum.php"></form>

However FormData() needs “An HTML <form> element“¹, not an array.

So if you are going to use the jQuery function, take the first element from it to get the reference to the form:

var forms = $('#submitalbum');
if (forms.length) {
    this.$http.post('addalbum.php', new FormData(forms[0]))

button elements don’t send value

A <button> is not a form input and hence there would not be a corresponding value in the form data. This if you want to check for form values, try checking for the artist, title, etc.

if(isset($_POST['artist'])) {
    echo json_encode($_POST);
}

If you really wanted to check if $_POST['submit'] is truthy, you could:

• add a hidden input:

  <input type="hidden" name="submit" value="1">
  

• convert the button to a submit button

  <input type="submit" name="submit" value="1">
  

• take the suggestion from this answer and manually append an entry to the form data

See a demonstration in this phpfiddle. Note that phpfiddle doesn’t allow multiple pages so the code from addalbum.php was placed at the top, and references to it were replaced with <?php echo $_SERVER['PHP_SELF'];?> (i.e. in the client-side code).

Missing parenthesis

Additionally, there is a missing parenthesis on the first line of the PHP code:

if(isset($_POST['submit']){

To correct this, add the missing closing parenthesis to close the expression:

if(isset($_POST['submit'])){

¹_{https://developer.mozilla.org/en-US/docs/Web/API/FormData/FormData}