[Bradski]

It's encryted code. I had the same thing happen a while back and I ended up re-uploading a fresh copy of WP (if that's what you use) several times. The "hacker" just kept burying similar code to yours deeper and deeper into my files till I eventually switched hosts which resolved the prob, I assume my hosts server had been compromised giving them free range to hack my files. It was very frustrating and I lost alot of traffic as a result!