Options +FollowSymlinks
RewriteEngine On
# deal with admin first
RewriteCond %{REQUEST_URI} ^/(admin)
RewriteRule ^admin/assets/(.*)$ backend/web/assets/$1 [L]
RewriteRule ^admin/css/(.*)$ backend/web/css/$1 [L]
RewriteCond %{REQUEST_URI} !^/backend/web/(assets|css)/
RewriteCond %{REQUEST_URI} ^/(admin)
RewriteRule ^.*$ backend/web/index.php [L]
RewriteCond %{REQUEST_URI} ^/(assets|css)
RewriteRule ^assets/(.*)$ frontend/web/assets/$1 [L]
RewriteRule ^css/(.*)$ frontend/web/css/$1 [L]
RewriteCond %{REQUEST_URI} !^/(frontend|backend)/web/(assets|css)/
RewriteCond %{REQUEST_URI} !index.php
RewriteCond %{REQUEST_FILENAME} !-f [OR]
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^.*$ frontend/web/index.php