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Asked: 2026-06-03T17:53:12+00:00

I’m trying to understand MVC, and learning CI framework. I’ve some questions about MVC

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I’m trying to understand MVC, and learning CI framework. I’ve some questions about MVC and some basic questions about CI.

1)Views are visual part of application as i read from tutorials, my question is: e.g There is a button “Login” but if user already logged in button will be “Logout”. Where will that login check be? On controller or on view? i mean

   //this is view//

     <?php if($_SESSION('logged') == true):?>
     <a href="logout">Logout</a>
     <?php else: ?>
     <a href="login">login</a>        
     <?php endif; ?>

or

  //this is controller//

 if($_SESSION('logged') == true)
 $buttonVal = 'logout';
 else
 $buttonVal = 'login';

 //and we pass these value to view like
 $this->view->load('header',$someData);

 //this time view is like
 <a href="<?=$somedata['buttonVal']?>"><?=$somedata['buttonVal']?></a>

i just write theese codes as an example i know they wont work, they are imaginary codes, but i guess you got what i mean. Login check should be on controller or on view?

2)Should models contain only codes about data and return them to controller? For example there is a math, we get 2 value from database and multiply them and display them. Model will multiply or controller will do it?

here we load data with model and do math on controller:
//model

   $db->query(....);
   $vars=$db->fetchAll();

   return $vars;

   //controller
   $multi = $vars[0] * $vars[1];
   $this-load->view('bla.php',$mutli);

here we load data with model and do math on model too, controller just passes data from model to view:

   //model

   $db->query(....);
   $vars=$db->fetchAll();
   $multi = $vars[0] * $vars[1];
   return $multi;

   //controller
   $multi = $this->model->multiply();
   $this-load->view('bla.php',$mutli);

i mean with that, models should do only database works and pass data to controllers, controller do rest of work and send view to render? Or models do work, controllers get them and send them to view?

3)This is about codeigniter, i have a header which has to be in every page, but it has javascripts,css depending to page i’m using

        <?php foreach ($styles as $style): ?>
        <link id="stil" href="<?= base_url() ?>/css/<?= $style ?>.css" rel="stylesheet" type="text/css" />
        <?php endforeach; ?>

this will be on every page, so in every controller i have 

$data['styles'] = array('css1','css2');
$this->load->view('header', $headers);

i’m thinking to make a main controller, write this in it, and all my others controllers will extend this, i see something MY_Controller on CI wiki, is this MY_Controller same with what i’m doing? Are there any other ways to do this?

Sorry for bad English and dummy questions. Thanks for answers.

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1 Answer

  1. Editorial Team

    This is absolutely view logic, the correct way to do it in my opinion:

     <?php if($logged_in):?>
 <a href="logout">Logout</a>
 <?php else: ?>
 <a href="login">login</a>        
 <?php endif; ?>

    The value of $logged_in would probably be retrieved from a call to a library method:

    <?php if ($this->auth->logged_in()): ?>

    Authentication is one of those things you’ll want access to globally, so you may be calling $this->auth->logged_in() in controller or views for different reasons (but probably not in models).

    In every controller i have

    $data['styles'] = array('css1','css2');
    $this->load->view('header', $headers);

    Yes you could extend the controller class with MY_Controller, but you’re better off keeping this in the view/presentation layer. I usually create a master template:

    <html>
<head><!-- load assets --></head>
<body id="my_page">
  <header />
  <?php $this->load->view($view); ?>
  <footer />
</body>
</html>

    And write a little wrapper class for loading templates:

    class Template {
  function load($view_file, $data) {
      $CI = &get_instance();
      $view = $CI->load->view($view_file, $data, TRUE);
      $CI->load->view('master', array('view' => $view));
  }
}

    Usage in a controller:

    $this->template->load('my_view', $some_data);

    This saves you from loading header/footer repeatedly. In my opinion, presentation logic like which CSS file to load or what the page title should be belongs in the view whenever possible.

    As far as models go, you want them to be reusable – so make them do what you need and keep it strictly related to data manipulation (usually just your database). Let your controller decide what to do with the data.

    Not related to MVC, but in general you want to write as little code as possible. Redundancy is a sign that you could probably find a better solution. These are broad tips (as is your question) but hopefully it helps.

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