How to prevent CI from reporting PHP Notice errors

I don't have much experience with CI, but I have inherited a project that uses it.

As the title says, how do you prevent CI from reporting PHP notice errors?

In the index.php file there's the following;

PHP Code:

switch (ENVIRONMENT) {
    case 'development':
        ini_set('display_errors', 1);
        ini_set('display_startup_errors', 1);
        error_reporting(E_ALL & ~E_NOTICE & ~E_STRICT & ~E_USER_NOTICE);
        break;
    case 'testing':
    case 'production':
        ini_set('display_errors', 0);
        if (version_compare(PHP_VERSION, '5.3', '>=')) {
            error_reporting(E_ALL & ~E_NOTICE & ~E_DEPRECATED & ~E_STRICT & ~E_USER_NOTICE & ~E_USER_DEPRECATED);
        } else {
            error_reporting(E_ALL & ~E_NOTICE & ~E_STRICT & ~E_USER_NOTICE);
        }
        break;
    default:
        header('HTTP/1.1 503 Service Unavailable.', TRUE, 503);
        echo 'The application environment is not set correctly.';
        exit(1); // EXIT_ERROR
}

I have checked that the environment is set to production, so PHP shouldn't be reporting notice errors, but for some reason CI is still displaying them?