Объект JavaScript неправильно отправляется в серверную часть

$("#newTabLink").click(function(e) {
      ntn++;
      console.info('ntn = ' + ntn + ' / id =' + id);
      id++;
      var tabData = new Object();
      var tc = $('#tabs').children().length;
      console.info('tc = ' + tc)
      tabData.label = 'New Tab ' + ntn;
      tabData.pos = tc;
      $.ajax({
        url: 'services/save_obj.php',
        type: 'POST',
        data: JSON.stringify(tabData),
        async: true,
        dataType: 'json',
        cache: false,
        contentType: "application/json; charset=utf-8",
        encode: true,

        success: function(response) {
          if (response.success == true) {
            id = response.id;
          } else if (response.success == false) {
            alert('Aww, something went wrong!');
          }
        }
        });
    });

<script src = "https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>