I have a complicate question which I can't find answers from online, or maybe I just don't know the best word to describe it,but hopefully you all and help out little bit, thanks you so much.
I want to create a user account system in php
I know how to store user date when they registra an account in form, but next time when people log in how do you know whether they has an account already or not, other words how do you validate their username and password when they come to your side.