Session issue

i m checking that session is exist or not like

if (Session::has('guest_user_chat_ids'))
        {
            echo 'if -----'.Session::get('guest_user_chat_ids');
        }
else
        {
            Session::put('guest_user_chat_ids', 'yusuf');
            echo 'else ==== '.Session::get('guest_user_chat_ids');
        }
        exit;

but always output of else part like "else ==== yusuf";