Why is it good save to save sessions in the database?

Question

I have seen that codeigniter have facility to save session values in database.
It says saving session in database is good security practice.

But I think saving

Answer 1

The idea is that sessions can't be hijacked.

A session ID is stored in a cookie. If a hacker can steal that ID, he can pretend to be someone else, because a session is identified by... it's ID.

By saving a user's session ID, IP and agent server-side (your database for example) you can compare the data saved in the database with the client. If a hacker steals someone's session ID, the hacker just might not have a matching IP and/or user-agent, making the users not match which allows you to show or hide certain content.

You have to compare the data manually though.