How i make a uniq id after login

Question

i wants make uniq id of person after sine up and log in

Answer 1

Concate username, e-mail, date of birth, sign up date/time and/or other information into a string, apply hash method on the string and save it as the user Id in the users table. Just an idea.

Hash function:
http://php.net/manual/en/function.hash.php