nginx with oauth
I don't have rep enough to comment so I'm quoting the solution since it's on the comments and can be missed easily.
THE PROBLEM IS SOLVED! Thank you, everyone. The problem was that we did not restarted php-frm service. When we manualy restarted it "/etc/init.d/php5-fpm restart" the error message was gone. – user1448914 Jun 11 '12 at 13:31
So if you are in the same situation as OP and me, this fixed it:
service php5-fpm restart