You can try this:
http://robertfrew.wordpress.com/2011...ging-in-nginx/
You might also have to make sure your PHP confiuration allows for error logging:
http://forum.nginx.org/read.php?2,14...947#msg-147947
catch_workers_output = yes might be required in your pool configuration:
http://nginx.2469901.n2.nabble.com/N...td7413282.html
But it is also possible that you use a buggy PHP version:
https://bugs.php.net/bug.php?id=61045