Code Igniter's Upload library is great, but doesn't allow you to upload multiple files. If you want to use the library, but need to do multiple file uploads, replace your /libraries/Upload.php file with this:
Upload.php

And here's how to do multiple uploads from your controller:

foreach ($_FILES["photo"]["error"] as $key => $error)
{								
	if($this->upload->do_upload("photo[$key]"))
	{
		$upload = $this->upload->data();
		
		// do stuff with your upload data here...
	}
	else
	{
		$data['upload_errors'] = $this->upload->display_errors('
', '
');
	}
}

Note: This will not affect your ability to do single uploads like you normally could.