htaccess redirect *.domain.com to www.domain.com/index.php

Question

I want to redirect a user to www.domain.com/index.php if they type in either: domain.com or www.domain.com. I'm clueless about htaccess. Here's what I found but I don't know how to write an OR statement for the www. redirect

RewriteEngine on
RewriteCond %{HTTP_HOST} ^domain\.com
RewriteRule (.*) http://www.domain.com/index.php$1 [R=301]

Answer 1

RewriteEngine on
RewriteCond %{HTTP_HOST} ^(domain\.com)(:80)? [NC]
RewriteRule ^(.*) http://www.domain.com/$1 [R=301,L]
DirectoryIndex index.php       
order deny,allow

Answer 2

Try this:

RewriteEngine on
RewriteCond %{HTTP_HOST} ^(www\.)?example\.com$
RewriteRule ^$ http://www.example.com/index.php [L,R=301]