This article applies to 123-reg servers running Plesk.
This article will explain how you can make php-fastcgi the default setting using Plesk 11.
Login to your Parallels Plesk Panel.
Click on the Domains link on the left panel.
Click on the Open in Control Panel link for the relevant domain name.
Click on the Website & Domains tab.
Click on the Show Advanced Operations option at the bottom of the page.
Click on the Website Scripting and Security icon.
Under the Web Scripting and Statistics section you will find the option for PHP support (run as), Select FastCGI application from the drop down list.
Click on the OK to save the change.