Creating Libraries

When we use the term "Libraries" we are normally referring to the classes that are located in the libraries directory and described in the Class Reference of this user guide. In this case, however, we will instead describe how you can create your own libraries within your application/libraries directory in order to maintain separation between your local resources and the global framework resources.

As an added bonus, Code Igniter permits your libraries to extend native classes if you simply need to add some functionality to an existing library. Or you can even replace native libraries just by placing identically named versions in your application/libraries folder.

In summary:

You can create entirely new libraries.
You can extend native libraries.
You can replace native libraries.

Storage

Your library classes should be placed within your application/libraries folder, as this is where Code Igniter will look for them when they are initialized.

Naming Conventions

File names must be capitalized. For example: Myclass.php
Class declarations must be capitalized. For example: class Myclass
Class names and file names must match.

The Class File

Classes should have this basic prototype (Note: We are using the name Myclass purely as an example):

<?php  if (!defined('BASEPATH')) exit('No direct script access allowed');




class Myclass {



    function some_function()

    {

    }

}


?>

Using Your Class

From within any of your Controller functions you can initialize your class using the standard:

$this->load->library('Mclass');

Where Myclass is the file name, without the ".php" file extension. You can submit the file name capitalized or lower case. Code Igniter doesn't care.

Once loaded you can access your class using:

$this->myclass->some_function();  // Object instances will always be lower case

Passing Parameters When Initializing Your Class

In the library loading function you can dynamically pass data via the second parameter and it will be passed to your class constructor:


$params = array('type' => 'large', 'color' => 'red');



$this->load->library('Myclass', $params);

If you use this feature you must set up your class constructor to expect data:

<?php  if (!defined('BASEPATH')) exit('No direct script access allowed');



// Initialize the class

$obj =& get_instance();

$obj->init_class('Myclass');



class Myclass {



    function Myclass($params)

    {

        // Do something with $params

    }

}


?>

You can also pass parameters stored in a config file. Simply create a config file named identically to the class filename.

Utilizing Code Igniter Resources within Your Library

To access Code Igniter's native resources within your library use the get_instance() function. This function returns the Code Igniter super object.

Normally from within your controller functions you will call any of the available Code Igniter functions using the $this construct:


$this->load->helper('url');

$this->load->library('session');

$this->config->item('base_url');

etc.

$this, however, only works directly within your controllers, your models, or your views. If you would like to use Code Igniter's classes from within your own custom classes you can do so as follows:

First, assign the Code Igniter object to a variable:

$obj =& get_instance();

Once you've assigned the object to a variable, you'll use that variable instead of $this:


$obj =& get_instance();


$obj->load->helper('url');

$obj->load->library('session');

$obj->config->item('base_url');

etc.

Note: You'll notice that the above get_instance() function is being passed by reference:

$obj =& get_instance();

This is very important. Assigning by reference allows you to use the original Code Igniter object rather than creating a copy of it.