Building a multi-user site - where to find the basics of the basics?

Question

Software design

There was a need to understand all the intricacies of building multi-user portals. How is the simplest authorization arranged? How is the user in the network, different from other users, how are the actions of individual users on the site initiated and how are the actions of individual users on the site divided - not registered and registered with different privileges?
Interested in the simple basics of the functioning of all this, it is possible with illustrative examples (standard solutions, concise architectural solutions), but most importantly - a detailed analysis of the individual stages, giving an idea of ​​​​the functioning and interaction of simple multi-user sites.
If anyone has seen sensible, exhaustive manuals on this issue - please share.

Answer 1

How is the simplest authorization arranged?

The public (login) and private (password) keys are checked. If they match, the user's identity is stored in the user's session.
It sends an HTTP request to you, and so it is.
A unique session value is generated for each user and stored in a cookie.
Initiated by the user with an HTTP request. Separated by different session IDs.
An access control system is being designed and implemented. There are 4 main types of implementation:
1. Checking the user's identification in the session, if it exists, it is authorized.
2. ACL
3. RBAC
4. Using external services like LDAP, OAuth,...
Any textbook on php from 700 pages.

Answer 2

Find in the book. Take any popular PHP+MySQL book and read.
A good example of a forum engine like phpBB

Answer 3

There was a need to understand all the intricacies of building multi-user portals.

And what, with single-user - have you already figured it out ?!)
There are two options:
1. If you have "checkers", then here is the site structure , of. a book on the PHP scripting language or the one that everyone has read: php-the-right-way
2. If "let's go" - put CMS Joomla! and implement on it (ask to freelance what is needed, although there are already a cloud of ready-made modules ).