Question

I want to create primary key like this…

http://www.example.com/download?d=NAPHMPWI

…i.e. the ?d=NAPHMPWI.

How can I do that?

Answer 1

Make the primary key an auto-incrementing integer, as most databases support out of the box. Display it as a string for your URLs by converting it to base 36 (which uses digits 0-9 and A-Z).

echo base_convert($id, 10, 36);

And convert URLs to database identifiers by converting from base 36 to base 10:

$id = base_convert($url_key, 36, 10);