Hit Counter in Codeigniter

I have the code below this:

(Step by step) 1. Put counter.txt in APPPATH . 'logs/counter.txt' 2. Make counter_helper.php set in APPPATH . 'helpers/counter_helper.php'; 3. Autoload newly created helper in APPPATH . 'config/autoload.php' file; 4. Make MY_Controller.php in APPPATH . 'core/MY_Controller.php' 5. Any controller should extend MY_Controller instead of CI_Controller; 6. Echo it on page with: count_visitor;?>

The Helper :

<?php defined('BASEPATH') OR exit('No direct script access allowed.');

if ( ! function_exists('count_visitor')) {
    function count_visitor()
    {
        $filecounter=(APPPATH . 'logs/counter.txt');
        $kunjungan=file($filecounter);
        $kunjungan[0]++;
        $file=fopen($filecounter, 'w');
        fputs($file, $kunjungan[0]);
        fclose($file);
        return $kunjungan[0];
    }
}

The Core :

<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');

class MY_Controller extends CI_Controller
{
    public $count_visitor;

    public function __construct()
    {
        parent::__construct();
        $this->count_visitor = count_visitor();
    }   
}

/* End of file MY_Controller.php */
/* Location: ./application/core/MY_Controller.php */

The Controller :

<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
class Home extends MY_Controller {
 public function index() {
 $data=array('isi'      =>'home/index_home');
 $this->load->view('layout/wrapper',$data); 
 }
}

The View :

<?php echo $this->count_visitor;?>

But there is something error in thats code. The error is like :