Setting $cookie_domain variable for specific folder structure During configuration of Ckeditor I have to setup the cookie domain variable. I have added my site in subfolder like www.example.com/mynewsitefolder, where www.example.com is my current and running site.
First I tried something like $cookie_domain = '.example.com/mynewsitefolder'; but that doesn't allow me to log in. 

How can I set it, so it works on a sub-folder?
The short answer is that you cannot set cookie domain to such a value. See http://www.php.net/manual/en/session.configuration.php#ini.session.cookie-domain

As a workaround, you can use this in settings.php (around where $cookie_domain is set:

$cookie_domain = ".example.com";
// Set cookie_path ourselves as Drupal doesn't.
ini_set('session.cookie_path', '/mynewsitefolder/');


$cookie_domain is eventually used to set session.cookie_domain but there is nothing in Drupal code base to set session.cookie_path and so we directly set that in settings.php itself.