You have a couple of options here - either by changing your relative links to properly reach up to the folder they are supposed to be in, or by changing the current working directory to the appropriate folder using the chdir() method. You could also use absolute paths.
How you should change your relative links is dependent on where in the directory structure you are accessing the file from...
Assuming you're hitting your blog file something like this:
http://www.site.com/blog/blog.php
And that your Admin folder is Inside the blog folder;
I would include the files like so:
include "admin/db.php";
include "admin/functions.php";
Again - assuming that both of these files are inside of the admin folder inside of the blog folder;
I.E. root/blog/admin/db.php
This is how I am interpreting what you are saying...