If you have not enabled PHP when creating the web hosting for your domain you will find that PHP scripts will not run (you may be shown the source of the script or your browser may prompt to download the file). To rectify this log in to your Plesk panel and follow the below steps:
Click on the Domains option on the left hand menu then click on your domain in the list of domain names
Click on the Web Hosting Settings icon on your Domain's home page
On the Web hosting setup for domain page scroll down to the services options then ensure the PHP tick box is ticked (ensure the safe_mode box is not ticked).
If you are still experiencing issues with PHP scripts not parsing then please log a ticket with the Dedicated Hosting Support team from your Namesco Online Control Panel