2.8.2.1. Instead of the results of PHP-scripts in the browser, their content is displayed

This could be due to directives in the .htaccess file that try to override the PHP handler. An example of such a directive: SetHandler php56-cgi.

To fix the situation, you should check the contents of the .htaccess file for such directives. If there are any, you must either comment them out by adding the symbol # to the beginning of lines with them, or delete.