Adding Values to Header Drupal 7 + .htaccess Well, I'm new to Drupal, I was wondering if I can add values to header?

Note: this is the code for my mysite.com

I got this piece of code in mysite.com

&lt;?php

    if (isset($_GET['code'])) {
    echo $_GET['code'];
    }

?&gt;


So for example, 

Drupal URL:

mysite.com/U2pVnWK

If I run that URL, it redirects me to PAGE 404

So I tried this, URL:

mysite.com/?code=U2pVnWK

Which it eventually works.

So I tried using RewriteRule thing in .htaccess and added this code

RewriteEngine on
RewriteRule ^([a-zA-Z0-9]+)$ index.php?code=$1


Even change it into

RewriteEngine on
RewriteRule ^([a-zA-Z0-9]+)$ ?code=$1


Also

RewriteEngine on
RewriteRule ^([a-zA-Z0-9]+)$ http://www.mysite.com/?code=$1


None of it works.

Plus I don't know where to put that piece of code in existing .htaccess that Drupal made it.

So to simplify, what I want is:

If I access mysite.com/U2pVnWK I would be able to retrieve and echo  U2pVnWK instead of redirecting to PAGE 404 PAGE

Any help would be appreciated. :)
There is something you can try with Drupal itself. 

hook_url_inbound_alter


  Alters inbound URL requests.


The idea is to drupal_lookup_path and if nothing found you can do whatever with $path variable in  hook_url_inbound_alter