Creating Core System Classes¶

System Class List¶

The following is a list of the core system files that are invoked every time CodeIgniter runs:

• Benchmark
• Config
• Controller
• Exceptions
• Hooks
• Input
• Language
• Loader
• Log
• Output
• Router
• Security
• URI
• Utf8

Replacing Core Classes¶

To use one of your own system classes instead of a default one simply place your version inside your local application/core/ directory:

application/core/some_class.php

If this directory does not exist you can create it.

Any file named identically to one from the list above will be used instead of the one normally used.

Please note that your class must use CI as a prefix. For example, if your file is named Input.php the class will be named:

class CI_Input {

}

Extending Core Class¶

If all you need to do is add some functionality to an existing library - perhaps add a method or two - then it’s overkill to replace the entire library with your version. In this case it’s better to simply extend the class. Extending a class is nearly identical to replacing a class with a couple exceptions:

• The class declaration must extend the parent class.
• Your new class name and filename must be prefixed with MY_ (this item is configurable. See below.).

For example, to extend the native Input class you’ll create a file named application/core/MY_Input.php, and declare your class with:

class MY_Input extends CI_Input {

}

class MY_Input extends CI_Input {

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

Tip: Any functions in your class that are named identically to the methods in the parent class will be used instead of the native ones (this is known as “method overriding”). This allows you to substantially alter the CodeIgniter core.

If you are extending the Controller core class, then be sure to extend your new class in your application controller’s constructors.

class Welcome extends MY_Controller {

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

        public function index()
        {
                $this->load->view('welcome_message');
        }
}

$config['subclass_prefix'] = 'MY_';