RewriteEngine On
# Only apply to URLs on this domain
RewriteCond %{HTTP_HOST} ^(www.)?domain.tld$
# Only apply to URLs that aren't already under folder.
RewriteCond %{REQUEST_URI} !^/public/
# Don't apply to URLs that go to existing files or folders.
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
# Rewrite all those to insert /folder.
RewriteRule ^(.*)$ /public/$1
# Also redirect the root folder.
RewriteCond %{HTTP_HOST} ^(www.)?domain.tld$
RewriteRule ^(/)?$ public/index.php [L]
