If you're looking to change PHP settings, it's the php.ini file you should be editing. It may be in /etc/php.ini, /etc/php/php.ini, /etc/php/apache2/php.ini, etc. Make sure you're changing the right one.
If you want to register global variabled you should set "register_globals= On", but it's not recommended for security reasons.
If you get parsing errors when trying a PHP script, are you sure the script actually works? Does the very same file work on other servers?