Message: Undefined variable: in View page

问题:

I am still new at PHP and the MVC concept. I have been trying to duplicate the CI News Tutorial(http://codeigniter.com/user_guide/tutorial/news_section.html), while using my own database and rewriting the code.

I have been unsuccessful.

Here is my controller:

    class Main extends CI_Controller
{

public function __construct()
{
    parent::__construct();

    $this->load->helper('url');
    $this->load->library('tank_auth');
    $this->load->model('structures_model');
}

public function structures()
{
    $this->load->model('structures_model');
    if (!$this->tank_auth->is_logged_in()) {
        redirect('/auth/login/');
    } else {
        $data['structures_all'] = $this->structures_model->get_structures();
        $this->load->view('templates/header', $data);
        $this->load->view('templates/navmain', $data);
        $this->load->view('structures', $data);
        $this->load->view('templates/footer', $data);
    }
}

Here is my model (structures_model)

<?php
class Structures_model extends CI_Model {

public function __construct()
{
    $this->load->database();
}

public function get_structures()
{
    $query = $this->db->get('structures');
    return $query->result_array();
}

}

And my view:

<?php foreach ($structures_all as $structures_info): ?>
<h2>Structures</h2>
<div id="main">
    <?php echo $structures_info['str_name'] ?>
</div>
<?php endforeach ?>

The error im getting is the common :

A PHP Error was encountered<
Severity: Notice
Message: Undefined variable: structures_all
Filename: main/structures.php
Line Number: 2

I am at a loss. I have looked at all the similar errors people have gotten, but can't figure out why exactly the structure_all array is not being defined. Shouldn't it get created in the controller function where I set :

$data['structures_all'] = $this->structures_model->get_structures();

What am I missing?

回答1:

The best way to debug this would be to assign $data['structures_all'] a definite array value, say: $data['structures_all'] = array('foo' => 'bar');

Is the $structures_all variable available in the view now? If it is available, you know that $this->structures_model->get_structures(); is returning null.

Do you have a table in your database called structures?

Are you sure your database connection details are filled out in config/database.php?

Do you have php error reporting set to all? There might be hidden messages... call error_reporting(E_ALL); in the constructor of your controller.

Also try echoing: $this->db->last_query(); to verify your query is being constructed the same way you tried in phpmyadmin...

Hopefully this puts you on the right track.