Codeigniter Different File Upload

$image_data = array();
$document_data = array();

// load library only once
$this->load->library('upload');

// image configuration
$image_config['upload_path'] = './uploads/';
$image_config['allowed_types'] = 'gif|jpg|png';
$image_config['max_size']    = '1000';
$image_config['max_width']  = '1024';
$image_config['max_height']  = '768';

$this->upload->initialize($image_config);

// process image upload first
if ( ! $this->upload->do_upload('image'))
{
   // image upload error , display error etc.
}
// image was uploaded properly, continue
else
{
   $image_data = $this->upload->data();

   // document configuration
   $document_config['upload_path'] = './uploads/';
   $document_config['allowed_types'] = 'pdf';

   $this->upload->initialize($document_config);

   if ( ! $this->upload->do_upload('document'))
   {
      // document upload error , display error etc.
      // you might need to delete the former uploaded image file ...
   }
   else
   {
      $document_data = $this->upload->data();
   }
}