Manual:Php.ini

php.ini is the PHP configuration file. This file will sometimes need to be modified; e.g. it might be necessary to set   if you get the error "Fatal error: Maximum function nesting level of '100' reached, aborting!" After you make changes, use   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

File location
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.