RewriteEngine On

RewriteBase /

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{QUERY_STRING} ^(.*)$
RewriteRule ^(.*)$ index\.php\?s=$1&%1 [L]
RewriteCond %{QUERY_STRING} ^(.*)$
RewriteRule ^(.*)/(.*)\.(htm|php)$ - [F]