This new post to Rudi's blog shows how, with the help of an external class you can use PHP to grab information from a torrent file.

To use this code you first need to include a file with the benc, bdec and hex2bin functions. To get the torrent data (like the announce url, the files etc) it is enough if we decode the content of the torrent. On the other hand, if we want to read the number of seeds, leechs and downloads, we must encode the info part of the torrent, encrypt it with the sha1 function and convert the result to lowercase.

He includes the code to make the decoding/encryption of the results a copy and paste away (once you have these functions to work from). He's even provided an example using the code that gets the information from a torrent on the Pirate Bay website.