where is my php.ini

Well it depends on the Linux distribution you are using, the version of php and the way you install it with Apache web server. Php.ini may be here:

/etc/php.ini

Or here:

/etc/php/php.ini
/etc/php5/php.ini

Or here:

/usr/bin/php5/bin/php.ini

Anyway, you can always find any file named php.ini in this manner

find / -name php.ini

The simplest yet most powerful usage of the renowned find command. By its help I was able to locate the php.ini on my Ubuntu 9.04 Apache2 and PHP5:

/etc/php5/apache2/php.ini