CodeIgniter comes with an “Auto-load” feature that permits libraries, helpers, and models to be initialized automatically every time the system runs. If you need certain resources globally throughout your application you should consider auto-loading them for convenience.
The following items can be loaded automatically:
1) Classes found in the libraries/ directory
2) Helper files found in the helpers/ directory
3) Custom config files found in the config/ directory
4) Language files found in the system/language/ directory
5) Models found in the models/ folder
To autoload resources, open the application/config/autoload.php file and add the item you want loaded to the autoload array. You’ll find instructions in that file corresponding to each type of item.
Do not include the file extension (.php) when adding items to the autoload array.
Additionally, if you want CodeIgniter to use a Composer auto-loader, just set $config[‘composer_autoload’] to TRUE or a custom path in application/config/config.php.