adding new library in CodeIgniter - php

Question

I've just started learning CodeIgniter, and I'm following this authentication tutorial by nettuts+. I did not understand one thing in it:
He added the following constructor code in the Welcome controller, which basically can be accessed only if the Session has variable username, otherwise it will redirect to admin controller.
function __construct()
{
session_start();
parent::__construct();
if ( !isset($_SESSION['username'])){
redirect('admin');
}
}
He said:
If you have multiple controllers, then
instead of adding the above code in
every controller, you should Create a
new library, which extends the
controller you will paste the code in,
and autoload the library into
project. That way this code runs
always when a controller is loaded.
Does it mean, I should
Create a file in application/libraries (eg. auth.php)
Paste this code in the auth.php
.
if ( !isset($_SESSION['username'])){
redirect('admin');
}
Now how to autoload this library and make it run every time a controller is loaded as he said?
Thanks

Answer 1

1) to autoload a library, just add it to the array in the file application/config/autoload.php, look for the 'library' section and paste the name of the library(without extension) there, as an element of the array.
$autoload['libraries'] = array ('auth');
2) I suggest you use the native session handler (session library), which works pretty well and avoids you to use php $_SESSION. You set a width $this->session->set_userdata(array('username' => 'User1', 'logged' => 'true'), and then you retrieve the values with $this->session->userdata['logged'], for ex.
Works like a charm and don't have to call session_start() and so on. Go check the help because it's really really clear on that.
3) As for your problem, I'll go, instead, for 'hooks'. There are different hooks, depending on their 'position', i.e. the moment in which you're calling them.
You can use, for ex.. the 'post_controller_constructor', which is called after controller initialization but BEFORE the methods, so it's in a midway between the constructor and the actual method. I usually insert this controls here.
You define hooks in application/config/hooks.php, and give them an array:
$hook['post_controller_constructor'] = array(
'class' => 'Auth',
'function' => 'check',
'filename' => 'auth.php',
filepath' => 'hooks',
'params' => array()
);
Anyway, for all these needs, the docs are pretty clear and straightforward, I suggest you read about hooks and session and you'll see everything gets much clearer!

Answer 2

The other way to do this. This is what he means in tutorial.
Create a library called MY_Controller in your application/libraries folder and extend it from CI_Controller:
Class MY_Controller extends CI_Controller {
public function __construct()
{
parent::__construct();
// do the stuff you want to execute on every page.
// like auth.
}
}
Autoload the auth class in autoload.php config file. There is no need to autoload MY_Controller CodeIgniter will automaticly recognise it and run it. You can also load the Auth library within MY_Controller
Extend your controllers with MY_Controller class. (Not CI_Controller)
Extending your controller will give to more control of your project. You can add extra methods to use everywhere on your project.
For more information about extending native libraries of CodeIgniter check Creating Libraries: CodeIgniter.

Answer 3

Add the new library to the autoload library array in config/autoload.php.
$autoload['libraries'] = array ('database', 'session', 'auth');
Then when you want to call the function in controller constructors use $this->auth->function_name();.
You may want to make it a hook if there's a lot of repeat functionality that you don't want to call in every single constructor.