AJAX call fails with SyntaxError: Unexpected end of JSON input

javascript php jquery ajax

PHP Snippet 1:

var data = {};
 data['rawFiles'] =$('#projectIDs').val(); 
 data['metadata'] = $('#getData').val();
  data['type']=  $('#submitType').val();
  data['pid']='csv';
   data['command']='data/qcTest'

PHP Snippet 2:

$.ajax({type: "POST", url: posturl, data: JSON.stringify(data), dataType: 'json'})