OS and server information:
I previously had php 5.3.x installed but decided to upgr
I came across this issue today and none of the solutions described worked for me. So here is another possible cause:
If you have something like
AddHandler x-mapp-php6 .php3 .php4 .php .phtml
in a .htaccess file of your web content folder, it can cause your PHP scripts to stop working. In my case the server did not know the x-mapp-php6 type, since that .htaccess file was something I imported from a different web host when I transferred the website content.
Just removing the AddHandler line from the .htaccess file solved it for me.