How to disable PHP Error reporting in CodeIgniter?

I've read the official documentation and all they say is that I should have a error_reporting() function located at the top of your main index.php file. But I don't have index.php file in my project. My base controller is called core so to get to main index I go to www.mysite.dom/core/. So I guess this error reporting function should be inside this controller? Then what I would like to know is where should I put it in the controller and what to put inside of it to disable the reporting. Thank you all for help, guess I am missing something :/
 

Here is the typical structure of new Codeigniter project:

- application/
- system/
- user_guide/
- index.php <- this is the file you need to change

I usually use this code in my CI index.php. Just change local_server_name to the name of your local webserver.

With this code you can deploy your site to your production server without changing index.php each time.

// Domain-based environment
if ($_SERVER['SERVER_NAME'] == 'local_server_name') {
    define('ENVIRONMENT', 'development');
} else {
    define('ENVIRONMENT', 'production');
}

/*
 *---------------------------------------------------------------
 * ERROR REPORTING
 *---------------------------------------------------------------
 *
 * Different environments will require different levels of error reporting.
 * By default development will show errors but testing and live will hide them.
 */

if (defined('ENVIRONMENT')) {
    switch (ENVIRONMENT) {
        case 'development':
            error_reporting(E_ALL);
            break;
        case 'testing':
        case 'production':
            error_reporting(0);
            ini_set('display_errors', 0);  
            break;
        default:
            exit('The application environment is not set correctly.');
    }
}

---