Pardon me, but your request is just wrong-headed.
You don't want to create *ANY* directories.
You want to detect the URL and *DYNAMICALLY* generate the content, based on your database values.
To get started, try something like
Now your bio.php
code can do
... make your DB connection ...
$user = $_GET["user"];
$sql = "SELECT * FROM user_information WHERE username='" . $user . "'";
$result = mysql_query($sql);
... now display data from the record (if any!) about that user ...
So you have *ONE* PHP page that generates bios for all members, on the fly.
[That code has some flaws in it...it was only for purposes of example.]
*LATER*, if you want to, you can learn how to use mod rewrite rules that will automatically convert, say,
to the (hidden) URL
so it *looks* like you have a directory per user all the while everything is done by one PHP page.