I apologize for the title is not so clear, but I will try to be better explaining. Basically I created a program that allows customers to an industry to make appointments through the web. This is working well but the main problem is the link sent via email. If you click this link, the user can change the appointment only if the user is logged in to the system. In fact, if the user has not logged in it is reported (by the email link) to the login page. So basically will:

**Email link:** `http:\www.website.com\Application\index\[appointment_hash]`  

**Redirect link:** `http\www.website.com\Application\`

Now the problem is that once logged I would redirect the user to the first link (`email link`) to load the details of the appointment. I'm working with CodeIgniter and I thought of the sessions, but considering that the user is not logged in I can not save any session, and then the link is lost anyway. There are many sites like Amazon and the like that save the link to an article even if you are not logged then ricaricaro later .. How can you do this? Hint?