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 versions or even 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:
- Benchmark
- Input
- Config
- Hooks
- Router
- URI
- Language
- Loader
- Controller
- Output
Replacing Core Classes
To use one of your own system classes instead of a default one simply place your version inside your local application/libraries directory:
application/libraries/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 function 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/libraries/MY_Input.php, and declare your class with:
class MY_Input extends CI_Input {
}
Note: If you need to use a constructor in your class make sure you extend the parent constructor:
class MY_Input extends CI_Input {
function My_Input()
{
parent::CI_Input();
}
}
Tip: Any functions in your class that are named identically to the functions 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.
Setting Your Own Prefix
To set your own sub-class prefix, open your application/config/config.php file and look for this item:
$config['subclass_prefix'] = 'MY_';
Please note that all native CodeIgniter libraries are prefixed with CI_ so DO NOT use that as your prefix.