EDITED, look at the end I got a Symfony 1.2 project, that was running on two domains (different app used on each domain) : www.mywebsite.com and abonnement.mywebsite.com I had two different cookie name/domain in each app. We decided to use the same cookie for both apps. So, i edited the config for both apps and set the cookie_domain to .mywebsite.com, and setted the cookie_name to mywebsite_cookie in boths apps. The problem is that when I visit abonnement.mywebsite.com, the old cookie is used. Manually deleting this cookie in my browser fixes the problem, but there are thousands of users on this website and I'm wondering if there's a solution to manually delete this cookie. I tried : if (isset($_COOKIE['abonnement_cookie'])) { ini_set('session.cookie_domain', 'abonnement.mywebsite.com); setcookie('abonnement_cookie', '', time() - 3600, '/'); $this->redirect('@internet_etape_1'); } But no success.