Laravel change get parameter in url string and return

I'm using get parameters for search filters, and need to be able to change a value of the query string variable and return the modified url (as a string variable, nothing fancy, no redirect or anything). This is what I have so far and what is happening:

public function index(Request $request){

    echo $request->fullUrl();
    // outputs http://ift.tt/2rEdyos

    $request->merge(['type' => 'anotherstring']);

    echo $request->fullUrl();
    // still outputs http://ift.tt/2rEdyos

    // is there a way to change a parameter value in the url and
    // return the modified url string?

}

I figure if worse comes to worse, I'll just parse the string manually, but it feels like there's a "laravel way" to go about this that I happen to be missing?

via Chebli Mohamed