Hello,
In order to upgrade PHP 5 to the needed version (if you would like to have other than shipped with Plesk) please do the following:
1) back up the directory %plesk_dir%\Additional\PleskPHP5 - just in case something will go wrong
2) stop the Plesk services (Control Panel and all that are included in the Plesk Run-Time section)
3) rename folder %plesk_dir%\Additional\PleskPHP5 to the orig_PleskPHP5
4) create a new folder PleskPHP5
5) download the needed version of PHP, unzip the content and copy it to the newly created folder PleskPHP5
6) copy the file php.ini from the old folder to the new one
7) start the services
8) click "Refresh" button in Components Management section in Plesk and check if you can see the new PHP version there
The only thing you need to be aware of is that other versions of PHP were not tested with Plesk 9 (the tested versions are shipped with Plesk).
Regards,
Maria