Getting PHP installed should be easy. OSX has it built in, linux you can just apt-get like BurningSky said. Windows you can install from
http://windows.php.net/download/ or XAMPP would work too like BurningSky said.
I just wanted to get something out there, thus the PHP script. Really, it is the trakt API calls that are interesting, the PHP script is just a proof of concept on how you can use them. Also planning to add similar calls for tv shows when I get a chance.
The focus of trakt is realtime scrobbling more than just mirroring your xbmc library. However, I do see the benefit of wanting your library synced and seeing what you've watched and haven't watched yet - that is why these API calls and php script are being created.
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Senne could be possible, but we haven't noticed any issues on our end. For me personally, I have a very low end ION system (single core, slowest proc) and it plays 1080p with no stuttering and trakt running.