Apache procurando por .html em vez de .php

Question

Eu configurei um servidor web no Linux. Tudo está funcionando bem se eu usar extensão .html. Quando eu mudo o DirectoryIndex no arquivo mij domain.conf e reinicio o apache / recarrego a configuração, ele ainda não funciona com a extensão .php.

#<VirtualHost *:443>
    # The ServerName directive sets the request scheme, hostname and port that
    # the server uses to identify itself. This is used when creating
    # redirection URLs. In the context of virtual hosts, the ServerName
    # specifies what hostname must appear in the request's Host: header to
    # match this virtual host. For the default virtual host (this file) this
    # value is not decisive as it is used as a last resort host regardless.
    # However, you must set it for any further virtual host explicitly.


#   ServerAdmin webmaster@localhost
#   DocumentRoot /var/www/html

    # Available loglevels: trace8, ..., trace1, debug, info, notice, warn,
    # error, crit, alert, emerg.
    # It is also possible to configure the loglevel for particular
    # modules, e.g.
    #LogLevel info ssl:warn

#   ErrorLog ${APACHE_LOG_DIR}/error.log
#   CustomLog ${APACHE_LOG_DIR}/access.log combined

    # For most configuration files from conf-available/, which are
    # enabled or disabled at a global level, it is possible to
    # include a line for only one particular virtual host. For example the
    # following line enables the CGI configuration for this host only
    # after it has been globally disabled with "a2disconf".
    #Include conf-available/serve-cgi-bin.conf
#</VirtualHost>


<Directory /var/www/html/domain.nu/public_html>
        Require all granted
</Directory>

<VirtualHost *:80>
        ServerName domain.nu
        ServerAlias domain.nu
        ServerAdmin webmaster@localhost
        DocumentRoot /var/www/html/domain/public_html/

        DirectoryIndex index.php index.cgi index.pl index.html index.xhtml index.htm

        ErrorLog /var/www/html/domain/logs/error.log
        CustomLog /var/www/html/domain/logs/access.log combined

        Redirect permanent / https://domain.nu/

</VirtualHost>

# vim: syntax=apache ts=4 sw=4 sts=4 sr noet

Desativei o arquivo 000-default.conf padrão e criei meu próprio arquivo domain.nu.conf para as configurações.