You would need to check your web host help pages or contact your web host to find out which php/php.ini handlers to use for your host server. Custom php.ini files are not a one size fits all thing and is a unique / specific thing to each web host and each web host server. This forum topic link below will get you started in the right direction. Disregard any references to BPS Pro custom php.ini setup.
http://forum.ait-pro.com/forums/topic/custom-php-ini-file-setup-php5-3-x/