Make index.html default, but allow index.php to be visited if typed in

By default, the DirectoryIndex is set to:

DirectoryIndex index.html index.htm default.htm index.php index.php3 index.phtml index.php5 index.shtml mwindex.phtml

Apache will look for each of the above files, in order, and serve the first one it finds when a visitor requests just a directory. If the webserver finds no files in the current directory that match names in the DirectoryIndex directive, then a directory listing will be displayed to the browser, showing all files in the current directory.

The order should be DirectoryIndex index.html index.php // default is index.html

Reference: Here.

I agree with @TheAlpha's accepted answer, Apache reads the DirectoryIndex target files from left to right , if the first file exists ,apche serves it and if it doesnt then the next file is served as an index for the directory. So if you have the following Directive :

DirectoryIndex file1.html file2.html

Apache will serve /file.html as index ,You will need to change the order of files if you want to set /file2.html as index

DirectoryIndex file2.html file1.html

You can also set index file using a RewriteRule

RewriteEngine on

RewriteRule ^$ /index.html [L]

RewriteRule above will rewrite your homepage to /index.html the rewriting happens internally so http://example.com/ would show you the contents ofindex.html .

If you're using WordPress, there is now a filter hook to resolve this:

remove_filter('template_redirect', 'redirect_canonical'); 

(Put this in your theme's functions.php)

This tells WordPress to not redirect index.php back to the root page, but to sit where it is. That way, index.html can be assigned to be the default page in .htaccess and can work alongside index.php.