If you want  to enable some php related settings by using php.ini file and  reflect it to all   directories under your account. Then follow the steps..

First create a php.ini file under the document root of your domain and change or add the default settings which you want or which is required for your domain.

for example :

allow_url_fopen = On
allow_url_include = On

then you need to add the following code in your .htaccess file. So you dont need to copy the php.ini file under each directories for changes to reflect.

SetEnv PHPRC “/home/username/public_html”