注销时出错(CodeIgniter）

用户可以正常登录，但当按下登出键时，会出现错误。然而，在下面，用户仍然登录，当再次按下注销按钮时，它实际上注销了（但仍然出现上面的错误）。有人能帮忙吗？错误如下。

严重性：警告

消息：无法修改标头信息-标头已由发送（输出开始于/customers/2/e/jessicarosedavidson.co.uk/httpd.www/codeigniter/application/models/Login_model.php：41）

文件名：Session/Session_driver.php

线路编号：110

回溯：

文件：/customers/2/e/jessicarosedavidson.co.uk/httpd.www/designener/application/controllers/Login.php行：59功能：session_delete

文件：/客户/2/e/e/jessicarosedavidson.co.uk/http://www/deigneter/index.php行：292功能：require_one

这是我的登录型号

 <?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
  class Login_model extends CI_Model {
    public function __construct()
    {
            $this->load->database();
    }
    public function login($email, $password)
    {
    $this->db->where("email",$email);
    $this->db->where("password",$password);
    $query=$this->db->get("mvc_user");
     if($query->num_rows()>0)
    {
        foreach($query->result() as $rows)
    {
//add all data to session
$newdata = array(
  'user_id'  => $rows->id,
  'user_name'  => $rows->username,
  'user_email'    => $rows->email,
  'logged_in'  => TRUE,
);
}
$this->session->set_userdata($newdata);
return true;
}
return false;
}
}
?>

这是我的控制器Login.php

<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
class Login extends CI_Controller{
    public function __construct()
    {
        parent::__construct();
         $this->load->model('login_model');
    }

    public function index()
    {
         if(($this->session->userdata('user_name')!=""))
    {
            $this->welcome();
    }
    else    {
         $data['title']= 'Login';
            $this->load->view('templates/header', $data);
            $this->load->view('templates/nav');
            $this->load->view('login/signin', $data);
            $this->load->view('templates/footer');
            }
    }

    public function welcome()
    {
        $data['title']= 'Welcome';
        $this->load->view('templates/header', $data);
        $this->load->view('templates/nav');
        $this->load->view('login/welcome', $data);
        $this->load->view('templates/footer');
    }

     public function login()
    {
        $email=$this->input->post('email');
        $password=$this->input->post('pass');

        $result=$this->login_model->login($email,$password);
        if($result) $this->welcome();
            else        $this->index();
    }
public function logout()
 {
  $newdata = array(
  'user_id'   =>'',
  'user_name'  =>'',
  'user_email'     => '',
  'logged_in' => FALSE,
  );
  $this->session->unset_userdata($newdata );
  $this->session->sess_destroy();
  $this->index();
  }

  }
  ?>

我的视图位于视图文件中一个名为login的文件中。任何帮助都将非常感谢，因为我是新的代码点火器！！