Customised Php.ini

There is a shared server running PHPSuexec, and we need to change some php settings, and therefore doing that in .htaccess is not possible.

We copied php.ini from /usr/local/lib/, made a modification and placed it in the web root path.

I thought that any settings that have been changed would 'propagate' throughout the rest of the website (i.e. all paths underneath the web root, in the heirarchy), but unfortunately, we have found out that this is not the case. The settings that were modified, were only reflected in the web root path.

Is there some method to ensure that the php modifications are reflected throughout the entire website ? We don't really want to have to place a copy of the entire (modified) php.ini in every path.