Move web root (document root) of a server to a subdirectory on Apache using .htaccess

.htaccess

# I had such a hard time finding this information, so I decided to keep it here.
# Change your server's pointing "example.com" from "/public_html/" to "/public_html/subdir" **without** changing the URL!

# URL remains the same, server directory changes
# Replace "example.com" with your domain and "subdir" with the directory your site is in.

<IfModule mod_rewrite.c>
  RewriteEngine on

  RewriteCond %{HTTP_HOST} ^(www.)?example.com$ [NC]
  RewriteCond %{REQUEST_URI} !^/subdir/
  RewriteRule ^(.*)$ /subdir/$1 [L]
</IfModule>

# For example, the URL "example.com/magical-dinosaur/" will remain the same.
# But your server will load "/public_html/subdir/magical-dinosaur/" as opposed to "/public_html/magical-dinosaur/"