When running PHP on Windows, the configuration
values can be modified on a per-directory basis using the Windows registry. The configuration values are stored in the registry key HKLM\SOFTWARE\PHP\Per Directory Values, in the sub-keys corresponding to the path names. For example, configuration values for the directory c:\inetpub\wwwroot would be stored in the key HKLM\SOFTWARE\PHP\Per DirectoryValues \c\inetpub\wwwroot. The settings for the directory would be active for any script running from this directory or any subdirectory of it. The values under the key should have the name of the PHP configuration directive and the string value. PHP constants in the values are not parsed. However, only configuration values changeable in PHP_INI_USER can be set this way, PHP_INI_PERDIR values can not.
For IIS : If you experience high parsetimes, try to set output_buffering to On. IIS has problems with scripts outputting many small pieces of text, and with output_buffering = On, PHP sends the whole page to IIS in one piece.