WordPress blogs show the same duplicate content for https://www.askapache.com/index.php and https://www.askapache.com/. If you've read about using a robots.txt file for WordPress SEO, than you already understand this setup results in Duplicate Content penalties being levied against your Blog and Web Site by Search Engines.
A common request is to be able to remove or redirect the index.php from appearing in the url. This is possible only with server-side technology like .htaccess configuration files or your main server config by using the Mod_Rewrite Rewrite Module.
The fix is a bit of clever .htaccess code utilizing mod_rewrite to only redirect index.php if the request for /index.php came from a client (e.g. browser or web robot), and not if the request is an internal redirect that apache does when / is requested so that it can serve the contents of index.php.
Options +FollowSymLinks
DirectoryIndex index.php
RewriteEngine On
RewriteBase /
RewriteCond %{THE_REQUEST} ^[A-Z]{3,9}\ /index.php HTTP/
RewriteRule ^index.php$ https://www.askapache.com/ [R=301,L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
Options +FollowSymLinks
DirectoryIndex index.php
RewriteEngine On
RewriteBase /blog/
RewriteCond %{THE_REQUEST} ^[A-Z]{3,9}\ /blog/index.php HTTP/
RewriteRule ^index.php$ https://www.askapache.com/blog/ [R=301,L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /blog/index.php [L]
The problem with this is that any request for "/" is internally rewritten to index.php by Apache mod_dir if you have index.php in the DirectoryIndex list (the usual set-up), so it's difficult to avoid an infinite loop.