.htaccess

Options +FollowSymlinks
RewriteEngine On

Options -Indexes
RewriteEngine on 

RewriteCond %{HTTP_REFERER} !^http://(www\.)?localhost [NC] 
RewriteCond %{HTTP_REFERER} !^http://(www\.)?localhost.*$ [NC] 
RewriteRule \.(gif|jpg|png|js|css)$ - [F]
ErrorDocument 403 http://localhost/404.html
ErrorDocument 404 http://localhost/404.html

# deal with admin first
RewriteCond %{REQUEST_URI} ^/yii2-advanced-quickstart/(admin)
RewriteRule ^admin/assets/(.*)$ backend/web/assets/$1 [L]
RewriteRule ^admin/css/(.*)$ backend/web/css/$1 [L]

RewriteCond %{REQUEST_URI} !^/yii2-advanced-quickstart/backend/web/(assets|css)/
RewriteCond %{REQUEST_URI} ^/yii2-advanced-quickstart/(admin)
RewriteRule ^.*$ backend/web/index.php [L]

RewriteCond %{REQUEST_URI} ^/yii2-advanced-quickstart/(assets|css)
RewriteRule ^assets/(.*)$ frontend/web/assets/$1 [L]
RewriteRule ^css/(.*)$ frontend/web/css/$1 [L]
RewriteRule ^js/(.*)$ frontend/web/js/$1 [L] 
RewriteRule ^images/(.*)$ frontend/web/images/$1 [L]

RewriteCond %{REQUEST_URI} !^/yii2-advanced-quickstart/(frontend|backend)/web/(assets|css)/
RewriteCond %{REQUEST_URI} !index.php
RewriteCond %{REQUEST_FILENAME} !-f [OR]
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^.*$ frontend/web/index.php