This is for Apache 2. It is in the /etc/apache2/httpd.conf file.
### Global Environment
######################################################
Include /etc/apache2/conf.d/php.conf
#
# The directives in this section affect the overall operation of Apache,
# such as the number of concurrent requests.
Also make sure you add the phpinfo.php script to your htdocs file so you
can test php.
Mike