Symfony 2.8 vhost: www/ directory instead of project index - symfony

Question

i started new project on symfony 2.8.2.
I added on my apache2 sites/enabled this vhost file, copied from symfony cookbook:
<VirtualHost *:80>
ServerName local.n-difference.fr
ServerAlias local.n-difference.fr
DocumentRoot /var/www/n-difference/web
<Directory /var/www/n-difference/web>
AllowOverride None
Order Allow,Deny
Allow from All
<IfModule mod_rewrite.c>
Options -MultiViews
RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^(.*)$ app.php [QSA,L]
</IfModule>
</Directory>
# uncomment the following lines if you install assets as symlinks
# or run into problems when compiling LESS/Sass/CoffeeScript assets
# <Directory /var/www/project>
# Options FollowSymlinks
# </Directory>
# optionally disable the RewriteEngine for the asset directories
# which will allow apache to simply reply with a 404 when files are
# not found instead of passing the request into the full symfony stack
<Directory /var/www/project/web/bundles>
<IfModule mod_rewrite.c>
RewriteEngine Off
</IfModule>
</Directory>
ErrorLog /var/log/apache2/errors.log
</VirtualHost>
I did sudo service apache2 restart to refresh the server.
I access the project from another Dev PC with ssh, and of course, i added on this etc/hosts file:
192.168.1.20 local.n-difference.fr
The problem is when i try to access the url local.n-difference.fr, i have this www/ index page
Did i forget something ?
Thank's a lot for your help :)
(and sorry for my bad english)