Code:
Options +FollowSymlinks
RewriteEngine on
RewriteRule ^index.php?$ /? [R=301]
The regular expression checking for your various index files means -
the file name string
^ (starts with) index.ph p? (followed by an optional p) $ (at the end - nb: query strings aren't matched and are normally automatically appended to the replacement)
The replacement file name string (not a regular expression)
/ (root) ? (discard any query strings)
The switch (not a regular expression)
[R=301] (Redirection - Moved Permanently)