Configure mod_rewrite to add "www" and to support MVC - php

Question

I would like to add www into the URL if the users forgot to type and still supporting MVC by redirecting to the index.php with [QSA]
This is my current working .htaccess
RewriteCond %{REQUEST_FILENAME} !-l
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^ index.php [L,QSA]
Using this .htaccess everything works fine, I can type www.abc.com/xxx/yyy to visit any specific pages
Anyway because I'm using Facebook authentication so I must prevent my users from typing the site URL without www, so I tried to edit my .htaccess
RewriteCond %{HTTP_HOST} ^abc\.com$
RewriteRule ^(.*)$ http://wwww.abc.com/$1 [R=301,QSA]
RewriteCond %{REQUEST_FILENAME} !-l
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^ index.php [L,QSA]
With this configuration if I typed abc.com I was redirected to www.abc.com, but if I typed abc.com/xxx/yyy I was only redirected as www.abc.com instead of being redirected to the specific page.
I also tried
# 1
RewriteCond %{HTTP_HOST} ^abc\.com$
RewriteRule ^(.*)$ http://wwww.abc.com/$1 [QSA]
# 2
RewriteCond %{HTTP_HOST} ^abc\.com$
RewriteRule ^(.*)$ http://wwww.abc.com/index.php [QSA]
# 3
RewriteCond %{HTTP_HOST} ^abc\.com$
RewriteCond %{REQUEST_FILENAME} !-l
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ http://wwww.abc.com/$1 [L,QSA]
None of them is working, please guide what to do
Thanks.

Answer 1

Add this 2 lines above your .htaccess file
RewriteCond %{HTTP_HOST} !^www\.(.*)$ [NC]
RewriteRule ^(.*)$ http://www.%{HTTP_HOST}/$1 [R=301,L]
so your final htaccess will look like this
RewriteCond %{HTTP_HOST} !^www\.(.*)$ [NC]
RewriteRule ^(.*)$ http://www.%{HTTP_HOST}/$1 [R=301,L]
RewriteCond %{REQUEST_FILENAME} !-l
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^ index.php [L,QSA]