.htaccess

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/$1 [L]
RewriteRule ^admin/js/(.*)$ backend/web/js/$1 [L]
RewriteRule ^admin/img/(.*)$ backend/web/img/$1 [L]

RewriteCond %{REQUEST_URI} !^/backend/web/(assets|css|js|img)/  
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/$1 [L]
RewriteRule ^js/(.*)$ frontend/web/js/$1 [L] 
RewriteRule ^img/(.*)$ frontend/web/img/$1 [L]

RewriteCond %{REQUEST_URI} !^/(frontend|backend)/web/(assets|css|js|img)/ 
RewriteCond %{REQUEST_URI} !index.php
RewriteCond %{REQUEST_FILENAME} !-f [OR]
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^.*$ frontend/web/index.php