RewriteEngine on

 DirectoryIndex index.php index.html index.htm

 RewriteCond %{HTTP_HOST} ^08sifu.com$
 RewriteCond %{REQUEST_URI} !^/
 RewriteCond %{REQUEST_FILENAME} !-f
 RewriteCond %{REQUEST_FILENAME} !-d
 RewriteRule ^(.*)$ /$1
 RewriteCond %{HTTP_HOST} ^08sifu.com$
 RewriteRule ^(/)?$ /index.php [L]

 RewriteCond %{HTTP_HOST} ^aa.981sf.com$
 RewriteCond %{REQUEST_URI} !^/aa.981sf.com/
 RewriteCond %{REQUEST_FILENAME} !-f
 RewriteCond %{REQUEST_FILENAME} !-d
 RewriteRule ^(.*)$ /aa.981sf.com/$1
 RewriteCond %{HTTP_HOST} ^aa.981sf.com$
 RewriteRule ^(/)?$ aa.981sf.com/index.php [L]