Beginner question

Hi guys, im new on auth0.
I already installed the framwork at my server.
Im successfully doing authentincation.
Then auth0 redirects to my callback url with two get params: code and state.
What should do with them ?
How can I get user info ?

Documentation mention the $auth0->getUser() call but can not make it work.
Any idea ? sample code ?
I just want to add simple user password authentication to my web page.

This question is duplicate and it was solved here.