CI_Router::_set_routing PHP Method

    protected function _set_routing()
    {
        // Load the routes.php file. It would be great if we could
        // skip this for enable_query_strings = TRUE, but then
        // default_controller would be empty ...
        if (file_exists(APPPATH . 'config/routes.php')) {
            include APPPATH . 'config/routes.php';
        }
        if (file_exists(APPPATH . 'config/' . ENVIRONMENT . '/routes.php')) {
            include APPPATH . 'config/' . ENVIRONMENT . '/routes.php';
        }
        // Validate & get reserved routes
        if (isset($route) && is_array($route)) {
            isset($route['default_controller']) && ($this->default_controller = $route['default_controller']);
            isset($route['translate_uri_dashes']) && ($this->translate_uri_dashes = $route['translate_uri_dashes']);
            unset($route['default_controller'], $route['translate_uri_dashes']);
            $this->routes = $route;
        }
        // Are query strings enabled in the config file? Normally CI doesn't utilize query strings
        // since URI segments are more search-engine friendly, but they can optionally be used.
        // If this feature is enabled, we will gather the directory/class/method a little differently
        if ($this->enable_query_strings) {
            // If the directory is set at this time, it means an override exists, so skip the checks
            if (!isset($this->directory)) {
                $_d = $this->config->item('directory_trigger');
                $_d = isset($_GET[$_d]) ? trim($_GET[$_d], " \t\n\r\v/") : '';
                if ($_d !== '') {
                    $this->uri->filter_uri($_d);
                    $this->set_directory($_d);
                }
            }
            $_c = trim($this->config->item('controller_trigger'));
            if (!empty($_GET[$_c])) {
                $this->uri->filter_uri($_GET[$_c]);
                $this->set_class($_GET[$_c]);
                $_f = trim($this->config->item('function_trigger'));
                if (!empty($_GET[$_f])) {
                    $this->uri->filter_uri($_GET[$_f]);
                    $this->set_method($_GET[$_f]);
                }
                $this->uri->rsegments = array(1 => $this->class, 2 => $this->method);
            } else {
                $this->_set_default_controller();
            }
            // Routing rules don't apply to query strings and we don't need to detect
            // directories, so we're done here
            return;
        }
        // Is there anything to parse?
        if ($this->uri->uri_string !== '') {
            $this->_parse_routes();
        } else {
            $this->_set_default_controller();
        }
    }

 function _set_routing()
 {
     parent::_set_routing();
     // re-routed url
     if ($this->uri->rsegments != $this->segments) {
         if (count($this->uri->rsegments) > 0) {
             array_unshift($this->uri->rsegments, $this->_route['directory']);
         }
     }
 }