Edit/update multiple file codeigniter

Dear Semua,

Saya membuat form multiple upload dengan 2 input file. Dimana user bisa memilih salah satu atau dua"nya untuk mengupload file. Namun saya kebingungan ketika melakukan update/edit pada model. Output yg diinginkan, user melakukan update pada file yang belum di upload. Adakah yang bisa membantu saya? Karena sebelumnya saya juga udh bertanya ke stackoverflaw namun belum ada respon hingga sekarang. Nuhun

View

<input type="file" id="file_tuton1" name="userfile[]">
<input type="file" id="file_tuton2" name="userfile[]">

Controller

$data = $this->input->post('id');
        $this->load->library('upload');

	    $dataInfo = array();
	    $files = $_FILES;
	    $cpt = count($_FILES['userfile']['name']);
	    for($i=0; $i<$cpt; $i++)
	    {
	        $_FILES['userfile']['name']= $files['userfile']['name'][$i];
	        $_FILES['userfile']['type']= $files['userfile']['type'][$i];
	        $_FILES['userfile']['tmp_name']= $files['userfile']['tmp_name'][$i];
	        $_FILES['userfile']['error']= $files['userfile']['error'][$i];
	        $_FILES['userfile']['size']= $files['userfile']['size'][$i];

	        $this->upload->initialize($this->set_upload_options());
	        $this->upload->do_upload();
	        $dataInfo[] = $this->upload->data();
	    }
	    $files = array(
	        'file_tuton1' 		=> $dataInfo[0]['file_name'],
	        'file_tuton2'		=> $dataInfo[1]['file_name'],
	        'userdatecreate' 	=> date('Y-m-d H:i:s')
	    	);
		    $result_set = $this->tuton_model->update_files($files, $data);
		    $this->session->set_flashdata('file_success', 'Upload File Berhasil!');
			redirect(base_url() . "tuton");

Model

function update_files($files, $id){
       $this->db->where('id_file', $id);
       $this->db->update('tuton', $files);
    }