I've written this SHA1 class in PHP quite a while ago but thought I might just put it up in case anyone's still interested in using it.

The code was ported from Branden Hall's SHA1 Secure Hash for Flash MX which in turn was based on a JavaScript implementation. You can download the code here, feel free to drop me a line if you're using it for a particular project that's always nice to know!

FYI, people running a PHP release above 4.3 can use the built-in sha1() and sha1_file() functions.