If you need to change the way your PHP is working you can do that using .htaccess.
Please, note that not all PHP options can be changed using .htaccess.
A list of options that can be changed using .htaccess file can be found at:
http://www.php.net/manual/en/ini.php#ini.list

The ones that can be changed with .htaccess are the ones marked with: PHP_INI_PERDIR or PHP_INI_ALL. The ones marked as PHP_INI_SYSTEM cannot be changed via .htaccess files.

The syntax is pretty simple:

php_flag [variable_name] [value]

For example if you need to turn off register_globals:

php_flag register_globals off

If you need to change the PHP include path:

php_value include_path ".:/usr/local/lib/php:/your_include/path"

The include_path string starts with a dot “.” And then each additional path is separated with a semi colon. (e.g. .:/path1:/path2:/path3)