How can I insert a long, random string into an Img Url
 

like this:
http://mofo-domain/DSK20070217063051...V/mofo-img.jpg

$solution = $PHP + .htaccess;

lotsa ways , depends on how your using it..

if you put an htacess in a folder called "stb" like this
RewriteEngine on
RewriteRule ^(.*)\.jpg http://www.yoursite.com/stb/img.php?in=$1 [nc]

then in img.php in the same folder

<?php
$ein = explode("/",$in);
$out = $ein[1];
header("Location: http://yoursite.com/secretfolder/$out.jpg");
?>

That would turn

yoursite.com/stb/jg7y7iyikuiu6ujk7/test.jpg
turn into
yoursite.com/secretfolder/test.jpg

All due props to smokey, but had to chime in - don't rely on the code above for anything valugely security related
By using Location, your brower makes the request to the 'secretfolder' - so finding out the secret folder is trivial. If that's not a problem, then you're sweet.

Would be much faster to do a plain rewrite, though..