apache VirtualDocumentRoot

virtual.conf

LogFormat "%h^__%v^_%V^_%l^_%u^_%t^_%r^_%>s^%b^_%{Referer}i^%{User-Agent}i" vhost

NameVirtualHost *:80

<Directory *>
    Options FollowSymLinks ExecCGI Includes MultiViews
    AllowOverride All
    AcceptPathInfo On
</Directory>

<VirtualHost *:80>
    ServerName localhost
    VirtualDocumentRoot /var/www/%0/html
    ErrorLog /var/log/apache2/error-common.log
    CustomLog /var/log/apache2/access-common.log vhost
    SetEnv APPLICATION_ENV staging
</VirtualHost>

# <VirtualHost *:80>
#     ServerName example.com
#     ServerAlias www.example.com
#     DocumentRoot /var/www/example.com/html
#     ErrorLog /var/log/apache2/error-example.com.log
#     CustomLog /var/log/apache2/access-example.com.log vhost
# </VirtualHost>

But www won't work with your config.