从两个单独的输入提交合并文件

I want to merge all files uploaded with two separated inputs and send them to server - as files are not sent through inputs anymore but as an object, how I should receive them on server?

<form action="test.php" method="post">
  <input type="file" value="files[]" name="files" id="files" multiple/>
  <input type="file" value="files2[]" name="files2" id="files2" multiple/>
  <a class="btn btn-default" id="merge">Merge</a>
</form>

js

$("#merge").on("click", function() {
  var data1 = $("#files")[0].files;
  var data2 = $("#files2")[0].files;

  var obj = $.merge( $.merge([], data1), data2);
  console.log(obj);      
});