Can't use session variable in routes.php file in codeigniter?

I am use following code to retrieve the session variable in routes.php

if($this->db_session->userdata('request_url')!="")
{
$route['user/(:any)'] = "search_user_name/redirect_url/".$_SESSION['request_url'];
$this->db_session->unset_userdata('request_url');
}
else {
    $route['user/(:any)'] = "search_user_name/index/$1";
}

the session variable would be set into template/header.php

$this-&开发者_StackOverflowgt;db_session->set_userdata('request_url', $_SERVER["SERVER_NAME"].$_SERVER["REQUEST_URI"]);

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You can not use db_session in routes.php because routes.php is parsed before db_session is loaded. Maybe you should create a base controller and redirect from the constructor of the base controller.

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Correct me if iam wrong. You can use hooks. Codeigniter user guide hooks

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You can use database in routes and put your routes url in database. Here is an example:

require_once( BASEPATH .'database/DB'. EXT );
$db =& DB();
$table2 =  $db->dbprefix.'lang';
$query2 = $db->get( $table2 );
$result2 = $query2->result();
foreach( $result2 as $row )
{   
    $fields = $db->list_fields($table2);
    $findme   = 'code';
    foreach($fields as $field):
        $pos = strpos($field, $findme);
        if($pos !== false and $row->$field != ''):
            $route[''.$row->$field.''] = 'main/setlang/$1';
        endif;
    endforeach;
}