如何从服务器销毁用户会话

I have a blogging website in which users can post their ideas. A user is posting some offensive things. I have already deactivated that user from admin but the problem is that I am still getting their posts.

After deeply analysing things and my current code I am pretty sure that the ban will take effect when user logs out from their current session.

So my question is how can I destroy session of that particular user without affecting other users.

I am using Php in backend.

You can use in session_destroy() function, or destory only one session..

Example:

unset($_SESSION['whatever']);