replace or append new Item id to sef url

[lara_19800]

Hello,
I am enabling default joomla sef. I am using two templates and given login url in both the templates. If I entered wrong credentials template switching because of Item id. How can I fix this issue without modifying controller.php
Other wise I want to replace Item id using pluing and redirt again. but I don't know how to replace the existing Item id or append new Item id to sef url.

$app = JFactory::getApplication();
if (!$_REQUEST['Itemid'] && $app->getName() == 'site') {
$_REQUEST['Itemid'] = $_SESSION['Itemid'];
unset($_SESSION['Itemid']);
$app->redirect($_SERVER['REQUEST_URI']);
}

If I use the above code the page is always redicting(the condition is always true) and displaying error.

Please post the solution.

[PaulMore]

What templates are you using?