Where is php.ini located?

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

Use phpinfo() to find out

Write a simple PHP file with the following content:

<?php phpinfo();

And upload it to your server and access it in your web browser to get a page like this:

PHP configuration file php.ini path