php.ini is the PHP configuration file.
This file will sometimes need to be modified; e.g. it might be necessary to set
xdebug.max_nesting_level = 200 if you get the error "Fatal error: Maximum function nesting level of '100' reached, aborting!" After you make changes, use
/usr/local/apache/bin/apachectl graceful to reload the config files without actually killing the webserver and starting it back up.
If you are looking to enable/disable upload settings see LocalSettings.php
Some PHP installations have 2 php.ini files, one for the php_sapi module that handles the web server requests, and another for the PHP command line binaries.
To find it for the command line binary, use
For the web module, create a sample php file with this content:
and access it from the web server. It should display a lot of information about your PHP installation, including the location of the php.ini file.