Creating Core System Classes

Every time CodeIgniter runs there are several base classes that are initialized automatically as part of the core framework. It is possible, however, to swap any of the core system classes with your own version or even just extend the core versions.

Most users will never have any need to do this, but the option to replace or extend them does exist for those who would like to significantly alter the CodeIgniter core.

Note

Messing with a core system class has a lot of implications, so make sure you know what you are doing before attempting it.

System Class List

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

Config\Services
CodeIgniter\Autoloader\Autoloader
CodeIgniter\Config\DotEnv
CodeIgniter\Controller
CodeIgniter\Debug\Exceptions
CodeIgniter\Debug\Timer
CodeIgniter\Events\Events
CodeIgniter\HTTP\CLIRequest (if launched from command line only)
CodeIgniter\HTTP\IncomingRequest (if launched over HTTP)
CodeIgniter\HTTP\Request
CodeIgniter\HTTP\Response
CodeIgniter\HTTP\Message
CodeIgniter\HTTP\URI
CodeIgniter\Log\Logger
CodeIgniter\Log\Handlers\BaseHandler
CodeIgniter\Log\Handlers\FileHandler
CodeIgniter\Router\RouteCollection
CodeIgniter\Router\Router
CodeIgniter\Security\Security
CodeIgniter\View\View
CodeIgniter\View\Escaper

Replacing Core Classes

To use one of your own system classes instead of a default one, ensure that the Autoloader can find your class, that your new class extends the appropriate interface, and modify the appropriate Service to load your class in place of the core class.

For example, if you have a new App\Libraries\RouteCollection class that you would like to use in place of the core system class, you would create your class like this:

<?php

namespace App\Libraries;

use CodeIgniter\Router\RouteCollectionInterface;

class RouteCollection implements RouteCollectionInterface
{
    // ...
}

Then you would add the routes service in app/Config/Services.php to load your class instead:

public static function routes(bool $getShared = true)
{
    if ($getShared) {
        return static::getSharedInstance('routes');
    }

    return new RouteCollection(static::locator(), config('Modules'));
}

Extending Core Classes

If all you need to is add some functionality to an existing library - perhaps add a method or two - then it’s overkill to recreate the entire library. In this case, it’s better to simply extend the class. Extending the class is nearly identical to replacing a class with one exception:

The class declaration must extend the parent class.

For example, to extend the native RouteCollection class, you would declare your class with:

<?php

namespace App\Libraries;

use CodeIgniter\Router\RouteCollection;

class RouteCollection extends RouteCollection
{
    // ...
}

If you need to use a constructor in your class make sure you extend the parent constructor:

<?php

namespace App\Libraries;

use CodeIgniter\Router\RouteCollection as BaseRouteCollection;

class RouteCollection extends BaseRouteCollection
{
    public function __construct()
    {
        parent::__construct();

        // your code here
    }
}

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.