Self-contained extensions and ini variable expansion
;; /usr/local/etc/php.ini
open_basedir = /usr/local/www/htdocs:/usr/local/lib/php

;; /usr/local/etc/php/mcrypt.ini
extension = mcrypt.so

;; /usr/local/etc/php/yahoo-sports.ini
open_basedir = ${open_basedir}:/tmp