Upload multiple files by clicking file upload again

How can I appended files to be uploaded when user clicks on the input upload button again?

I have no problems with selecting multiple files to upload as I have set the multiple attribute. It is just when user wants to add more files to be uploaded.

Here's a scenario to better illustrate.

1. User clicks on file upload button.
2. User selects multiple files to upload.
3. User clicks on file upload button again.
4. User selects more files to upload.
5. User clicks on the upload to server button to upload files on the server.

Upon checking the request, it seems that the last batch are the only ones being uploaded. Shouldn't it be appended?

via Chebli Mohamed