Q:

Using backreference after RewriteCond in htaccess

I have:
RewriteCond %{HTTP_HOST} ^my.domain.com$ [NC]
RewriteRule ^(.*)$ index.php?q=search&keyword=$1

Input:
my.domain.com/foo_bar

I want: 
index.php?q=search&keyword=foo_bar

But in fact:
index.php?q=search&keyword=index.php

I don't understand why. Please help me!

A:

Your rewrite rule is actually rewriting twice, once for /foo_bar and second time for index.php as .* matches anything.
You just need to add 2 conditions to stop rewrite for files and directories:
# handle landing page
RewriteCond %{HTTP_HOST} ^my\.domain\.com$ [NC]
RewriteRule ^/?$ index.php?q=search [L,QSA]

# handle /foo_bar
RewriteCond %{HTTP_HOST} ^my\.domain\.com$ [NC]
# If the request is not for a valid directory
RewriteCond %{REQUEST_FILENAME} !-d
# If the request is not for a valid file
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^(.+)$ index.php?q=search&keyword=$1 [L,QSA]

