I did not get it work. I decided to write my own bot. When i finished the Server gave me a "nonce to small error" which can be interpreted as "your privat key and secret key are already in use". Which was not done by my own program and the key was only used for the php bot. I deleted the old keys, created a new one and everything worked as it should.
Any idea how or why that happened ?
Maybe bitfinex is binding keys to one single application, storing all the details about the sending computer, browser and so on? Though you might better ask that in bitfinex services thread.
https://bitcointalk.org/index.php?topic=229438