How to competently implement authorization in php, mySQL?

Question

Hashing

In search of useful information, I constantly came across the fact that the user's token is done through md5, for example md5(username.salt) . Why do they do it? After all, there is a collision that can always happen, especially on popular sites. How to implement it correctly. And what is the generally accepted way here. Thanks for the help!

Answer 1

After all, there is a conflict

which? Do not confuse identifier and token. The first must be unique, the second must not.