CodeIgniter userdata对于Session不起作用

Question

I am trying to create a blog site , i have a database named ci_test it has two table users and article . I have an issue with the session that can't fix. I set-

$config['encryption_key'] = '1234';

Also, set the property

$autoload['libraries'] = array('database','session');

But it gives the error :

Severity: Notice

Message: Undefined property: Admin::$session

Filename: controllers/admin.php

Line Number: 18

My login code is:

<?php

class Login extends MY_Controller{

    public function index()
    {
        $this->load->helper('form');
        $this->load->view('public/admin_login');
    }

        public function admin_login()
    {
        $this->load->library('form_validation');

        $this->form_validation->set_rules('username','user name','required|alpha|trim');
        $this->form_validation->set_rules('password','password','required');

        $this->form_validation->set_error_delimiters('<p class="text-danger">','</p>');

        if($this->form_validation->run())
        {

            $username = $this->input->post('username');
            $password = $this->input->post('password');

            $this->load->model('loginmodel');
            $login_id = $this->loginmodel->login_valid($username, $password);
            if($login_id)
            {
                //$this->load->library('session');
                $this->session->set_userdata('user_id', $login_id);

                redirect('admin/dashboard');
            }
            else{
                echo 'password dont'; 
            }

        }
        else
        {
            $this->load->view('public/admin_login');
        }


    }
}

Updated from comment login model

class Loginmodel extends CI_Model{ 

public function login_valid($username, $password) {

$q = $this->db->where(['uname'=>$username,'pword'=>$password])->g‌​et('users'); 

if($q->num_rows()) { 

return $q->row()->id; //return TRUE; } else{ return FALSE; 

} 

}

admin controller:

<?php

class Admin extends CI_Controller{

    public function dashboard()
    {


        $this->load->model('articlesmodel','article');

        $articles = $this->article->articles_list();

        $this->load->view('admin/dashboard',['articles'=> $articles]);
    }

    public function __construct()
    {
        if(! $this->session->userdata('user_id'))
        {
            redirect('login');
        }       
    }


}

Model:

<?php

class Articlesmodel extends CI_Model{

    public function articles_list()
    {

        $user_id = $this->session->userdata('user_id');
        $query = $this->db->select('title')->where('user_data',$user_id)->get('articles');

            return $query->result();        
    }


}

view:

<div class="container">
    <table class="table">
    <thead>
        <tr>
            <td>Serial no</td>
            <td>Article List</td>

            <td>#</td>
        </tr>
    </thead>
    <tbody>
<?php if(count($articles)): ?>
    <?php foreach($articles as $article): ?>
        <tr>
            <td>
                1
            </td>
            <td>
            <?= $article->title; ?>
            </td>

            <td>
                <a class="btn btn-primary">Edit</a>
                <a class="btn btn-danger">Delete</a>
            </td>
        </tr>
    <?php endforeach;?>
    <?php else:?>
        <tr>
            <td colspan="3">Record not found</td>
        </tr>
<?php endif;?>  
    </tbody>
</table>
</div>

Answer 1

Make sure your file name is controllers/Admin.php instead of controllers/admin.php first letter always upper case only same applies for classes

And your construct() should all ways be below class and you are missing parent::__construct()

<?php

class Admin extends CI_Controller {

    public function __construct() {
        parent::__construct(); // Missing
        if(! $this->session->userdata('user_id'))
        {
            redirect('login');
        }       
    }

    public function dashboard() {

    }

}

I think you have set it in a group. where user_id is group name

$data = array(
    'id' => $login_id->column_name
);

$this->session->set_userdata('user_id', $data);

Accessing data

$id = $this->session->userdata('user_id');

$id['id'];

Or Try

$this->session->set_userdata(array('user_id' => $login_id->column_name)); // 

http://www.codeigniter.com/user_guide/libraries/sessions.html#adding-session-data

Make sure if your using files in Ci3 you have set your path

$config['sess_cookie_name'] = 'ci_sessions';
$config['sess_expiration'] = 7200;
$config['sess_save_path'] = FCPATH . 'application/cache/session/';

Codeigniter Encryption Key http://randomkeygen.com/

$config['encryption_key'] = 'YyO29izmGbTj84kQPAkxkjI1Cz4Whe71';

Update

public function login_valid($username, $password) {
    $this->db->where('uname', $username);
    $this->db->where('pword', $password);
    $query = $this->db->get('users');

    if ($query->num_rows() == 1) {
        return $query->row();
    } else {
        return false;
    }
}

Then on the controller if login correct

$login = $this->some_model->login($this->input->post('username'), $this->input->post('password'));

if ($login) {
    $this->session->set_userdata(array('user_id' => $login->column_name));
    redirect('successcontroller');
} else {
     // Error
}

Answer 2

$config['encryption_key'] = '1234';

That isn't going to work because CodeIgniter has requirements for it's encryption_key. See the docs here.

https://codeigniter.com/userguide3/libraries/encryption.html

Try this

$key = $this->encryption->create_key(16);

And then use that key below

$config['encryption_key'] = 'YOUR KEY';

Alternatively, and even better, here's two websites that will generate CodeIgniter encryption keys for you.

http://jeffreybarke.net/tools/codeigniter-encryption-key-generator/

http://randomkeygen.com/