php - does this code guarantee a Unique id -

i'm trying create unique id that's random. solution suggested, i'm not if it's guaranteed they'll unique.

function uid($n) {     $id_part = base_convert($n, 10, 36);     $rand_part = str_shuffle('abcdefghijklmnopqrstuvwxyz0123456789');     return sprintf("%05s%.15s", $id_part, $rand_part); } 

the code uses unique id database auto-incremented id (that's $n input i'm guessing), fill characters added. gives supposedly "unique" 5 chars base-36 primary id + 15 rubbish chars. can confirm if result indeed unique ids or not.

to answer question, doing exactly. need give users unique id, doesn't directly equal user id in database. way user 1 not know registered before user 2, each user still has have unique "front id".

you can try inbuilt functionalities :

http://php.net/manual/en/function.uniqid.php

http://php.net/manual/en/function.com-create-guid.php

depends how uniqueness want have. if application, or globally.

globally guid better option.