To Enable and Disable Script Support ( php / cgi / apache ) in Plesk, Please follow the following settings:-
1) Login to Plesk control panel.

2) Click on "Websites and Domains"

3) Click on the "Domain Name" under whom you want to enable PHP support.

4) Click on Check box in front of "Disable / Enable PHP Scripting ( PHP / CGI / APACHE )

5) Click on "OK" once you have enabled the PHP support.
