Getting query string in Codeigniter

[eluser]OneCorea[/eluser]
Thanks a lot wiredesignz!!!

Well, how can I get a query string value in the URL when the sequence order of the id and value vary?

Such CI class library like '$this->uri->segment(n);',
$this->uri->uri_to_assoc(n, $uri_key);, I must set the $uri_key;

Is there some method to get the URL value in the URI address, which its URL parameter value vary?