How to do that Apache rewrite thingy where everything goes to index.php except static assets

.htaccess

# secure htaccess file
<Files .htaccess>
 order allow,deny
 deny from all
</Files>

RewriteEngine on
# redirect everything to index.php, except files in /a and index.php
RewriteCond %{REQUEST_URI} !(a/|index\.php)
RewriteRule (.*) index.php?%{QUERY_STRING}&request_uri=$1