How to remove PHP X-Powered-By?

[etrader]

I add custom X-Powered-By with "add_header X-Powered-By custom;"

However, when serving PHP fastcgi in the location, PHP X-Powered-By will
also be added to make the X-Powered-By as

X-Powered-By: PHP/5.3.3-1ubuntu9.10 custom

How can I totally remove PHP X-Powered-By to have my own custom one
only?

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,224706,224706#msg-224706