How to retrieve $config['myConfig_array'] in Code Igniter - codeigniter

Question

I've followed Codeigniter language and all seems to be setup as a hook.
function pick_language() {
require_once(APPPATH.'/config/language.php');
session_start();
// Lang set in URL via ?lang=something
if(!empty($_GET['lang']))
{
// Turn en-gb into en
$lang = substr($_GET['lang'], 0, 2);
$_SESSION['lang_code'] = $lang;
}
// Lang has already been set and is stored in a session
elseif( !empty($_SESSION['lang_code']) )
{
$lang = $_SESSION['lang_code'];
}
// Lang has is picked by a user.
// Set it to a session variable so we are only checking one place most of the time
elseif( !empty($_COOKIE['lang_code']) )
{
$lang = $_SESSION['lang_code'] = $_COOKIE['lang_code'];
}
// Still no Lang. Lets try some browser detection then
else if (!empty( $_SERVER['HTTP_ACCEPT_LANGUAGE'] ))
{
// explode languages into array
$accept_langs = explode(',', $_SERVER['HTTP_ACCEPT_LANGUAGE']);
log_message('debug', 'Checking browser languages: '.implode(', ', $accept_langs));
// Check them all, until we find a match
foreach ($accept_langs as $lang)
{
// Turn en-gb into en
$lang = substr($lang, 0, 2);
// Check its in the array. If so, break the loop, we have one!
if(in_array($lang, array_keys($config['supported_languages'])))
{
break;
}
}
}
// If no language has been worked out - or it is not supported - use the default
if(empty($lang) or !in_array($lang, array_keys($config['supported_languages'])))
{
$lang = $config['default_language'];
}
// Whatever we decided the lang was, save it for next time to avoid working it out again
$_SESSION['lang_code'] = $lang;
// Load CI config class
$CI_config =& load_class('Config');
// Set the language config. Selects the folder name from its key of 'en'
$CI_config->set_item('language', $config['supported_languages'][$lang]['folder']);
// Sets a constant to use throughout ALL of CI.
define('CURRENT_LANGUAGE', $lang);
}
Now when I try to access $config['supported_languages'] it returns null or errors. Why?