Use this command php -i | grep php.ini
It should show something below:
Configuration File (php.ini) Path => /etc
Loaded Configuration File => /etc/php.ini
/etc/php.ini is the server wide file, you can however edit it per site by editing: /etc/httpd/conf.d/vhost_domainname.com.conf
PHP 5.x:
<IfModule mod_php5.c>
php_admin_flag engine On
</IfModule>
PHP 3.x (we Think) & 4.x:
<IfModule mod_php4.c>
php_admin_flag engine On
</IfModule>
</IfModule>