$config['base_url'] = ((isset($_SERVER['HTTPS']) && $_SERVER['HTTPS'] == "on") ? "https" : "http");
$config['base_url'] .= "://".$_SERVER['HTTP_HOST'];
$config['base_url'] .= str_replace(basename($_SERVER['SCRIPT_NAME']),"",$_SERVER['SCRIPT_NAME']);

http://codeigniter.com/wiki/Automatic_configbase_url/

More info found in the link above, basically, you can replace the $config['base_url'] to the snippet below and you no longer need to set the base url. Useful for making your application more portable.

CodeIgniter Automatic Base URL Configuration

php, codeigniter

PHP