Free PHP URL shortener script that can shorten over 4 billion URLs

Hi, looks like it was a fun project. While you save yourself from checking the DB for a duplicate hash with your hex id strategy, a side effect of this technique is that every URL created with your service is effectively public. For instance, I could start at http://briancray.com/tests/shorturl/0 and work my way up through every URL ever shortened by incrementing the id in hex. Whether this is a vulnerability or undocumented feature is up to you to decide :)

I bring it up because I ran across the same issue with my own site, droplink.me. It was a more serious problem for me, because user uploaded files are supposed to be private. I went with randomly generated URLs.

the urls could be much shorter if you used a-z and A-Z and not just hex (a-f). But it saves some lines of code.