Displaying same page differently for users with different roles

I wanted some suggestions from someone with experience in php.

I am making a website in php which will have 4 kinds of users : 1. guest(unregistered), 2. registered, 3. registered with special privilages, 4. admins

So the same page will be visible differently to all four of them.

Right now I am doing that by using if conditions. In every page, I am checking the role of the user and开发者_如何学Go then using many if statements to display the page accordingly.

It makes the code very big and untidy and I have to check conditions again and again in all the pages.

1. Is there a better way to do this?

2. How is this done in big professional websites?

3. Extended Question: What is the most optimal way to do the same using a MVC framework like kohana 3.1? Does it have anything to do with acl?

It really depends on what you need.

For example if the page has big part that change completely, what I would suggest is to create different templates and include them depending on their "permissions"

 $permission = $_SESSION['type_user'];
 include '/path/to/file/with/permission/'.$permission.'/tpl.html';

and have something in the page similar to

<?php
//inside include.php you have the line similar to
//$permission = isset($_SESSION['type_user']) && $_SESSION['type_user']!=''?$_SESSION['type_user']:'common';
require_once '/mast/config/include.php';
include '/path/to/file/with/permission/common/header.html';
include '/path/to/file/with/permission/'.$permission.'/tpl_1.html';
include '/path/to/file/with/permission/common/tpl_2.html';
include '/path/to/file/with/permission/'.$permission.'/tpl_3.html';
include '/path/to/file/with/permission/common/footer.html';
?>

if the script is full of small parts like "show this text", or "show this button", you can create a function that will check the permissions for you

<?php
function can_user($action, $what){
   switch($action){
      case 'write':
          return $your_current_if_on_what;
          break;
      case 'read':
      default:
          return $your_current_if_on_what;
          break;
   }
}
?>

and the template will look like:

[my html]
<?=can_user('read','button')?'My Button':''?>
[my html]

As a rule of thumb, if a piece of code is used more than 2 times, it needs to be put in a function/file separately, so if you have many "IFS" you need to create a function