URL output

I can see that processing.php maybe cotains some sort of code, with url options:

$splitPath = explode ('/', $parsedURL['path']); 

        $str = get_option("siteurl")."/".$splitPath[2] ."/?".(!isset($_GET['page_id'])?"page_id=".$post->ID."&":"")."linkdir=".$type.(!empty($id)?"&_id=".$id:"");
        //default url
        //?post_id=2&linkdir=cat&_id=2&page_id=2#linkdir

        //seo url
        //?post_id=2&linkdir=cat&_id=2#linkdir
        foreach($_GET as $key => $val){
                if($key!="linkdir"&&$key!="_id"&&$key!="_page"){
                        $str .= "&".urlencode($key)."=".urlencode($val);
                }
        }
        return $str.(!empty($page)?"&_page=".$page:"")."#linkdir";

}

But i dont know how or if it’s possible to change the urls anywhere on the site or in the code or htaccess with mod_rewrite