How to access data sent by AJAX to a PHP file?

Question

I have this droppable Jquery along with two pieces of data I want to send to a PHP file when the object gets dropped:

 $( function() {
    $( ".draggable" ).draggable();
    $( ".droppable" ).droppable({
      drop: function( event, ui ) {
         var playerid = ui.draggable[0].getAttribute("data-playerid");
         var value = jQuery(this).data('value');
          console.log(playerid);
          console.log(value);
        $( this )
          .addClass( "ui-state-highlight" )
          .find( "p" )
            .html( "Dropped!" );
         $.ajax({
            type: "POST",
            contentType: 'application/json; charset=utf-8',
            url: "ajax-update-value.php",
            data: {playerid:playerid, value:value},
            success: function(result) {
            // do something with the result of the AJAX call here
                alert(result);
            }
        });
      }
    });
  });

And in the PHP file, I want to use those two specific values to update my MySQL database. I have this below, but it's not pulling in the values, so I'm obviously doing something wrong/stupid. What is the proper way to access the two pieces of data?

$playerid=$_POST['playerid'];
$value=$_POST['value'];