How to prevent multiple logins in PHP website

Question

I want to prevent multiple logins in a php application.

First, I create login status (active, notactive) in a user table.

When user A logs in the user status

Answer 1

You need to create a unique ID and store that in a database. What I did was create too. I store one in a session variable and use that to prevent session hijacking and another in a database to prevent multiple logins. The following code will create a unique ID:

$unique_id = sha1('xzr4'.gethostbyaddr($_SERVER['REMOTE_ADDR']).$random_string.$_SERVER['HTTP_USER_AGENT'].'f8k2');

If the unique ID doesn't match, you simply log the user out.