How to make CodeIgniter accept "query string" URLs?

According to CI's docs, CodeIgniter uses a segment-based approach, for example:

example.com/my/group

If I want to find a specific group (id=5), I can visit

example.com/my/group/5

And in the controller, define

function group($id='') {
    ...
    }

Now I want to use the traditional approach, which CI calls "query string" URL. Example:

example.com/my/group?id=5

If I go to this URL directly, I get a 404 page not found. So how can I enable this?

For reliable use of query strings I've found you need to do 3 things

1. In application/config/config.php set $config['enable_query_strings'] = true;
2. Again in application/config/config.php set $config['uri_protocol'] = "PATH_INFO";
3. Change your .htaccess to remove the ? (if present) in the rewrite rule

I use the following

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php/$1 [L]