How to make CodeIgniter accept "query string" URLs?

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} !-fRewriteCond %{REQUEST_FILENAME} !-dRewriteRule ^(.*)$ index.php/$1 [L]

//Add this method to your (base) controller :protected function getQueryStringParams() {    parse_str($_SERVER['QUERY_STRING'], $params);    return $params;}// Example : instagram callback actionpublic function callback(){    $params = $this->getQueryStringParams();    $code = !empty($params['code']) ? $params['code'] : '';    if (!empty($code))    {        $auth_response = $this->instagram_api->authorize($code);        // ....      }    // .... handle error}    

This might help some people; put this into your controller's constructor to repopulate $_GET on a controller-by-controller basis (e.g. if you are integrating a third party lib that relies on $_GET - such as most PHP OAuth libraries).

parse_str(str_replace($_SERVER['QUERY_STRING'],'',$_SERVER['REQUEST_URI']),$_GET);