Theory and practice of multilingual sites, what can you read / watch?

Question

Internationalization and localization

Hello!
I mainly make multilingual sites in php+MySQL.
I solve the problem head-on: there are pages / resources / pieces of information that are presented in different language versions, the task is to link them together and display them at a specific URL.
But I want to find beautiful and effective solutions, if they exist.
Please recommend good material from the best practice series.
Interested in all sorts of solutions, ideas and implementations.
Not ready-made plugins and additions to the CMS, namely, general algorithms and patterns that can be applied without being tied to a specific programming language or CMS.
Thanks in advance!

Answer 1

See how it's done in Symfony 2 and Yii 2

Answer 2

I liked this article as a starting point on what options there might be:
https://codex.wordpress.org/Multilingual_WordPress