The [[ https://secure.phabricator.com/book/phabricator/article/configuration_guide/ | Configuration Guide ]] appears to be missing an important step for `apache2`.
Perhaps this is just a difference between using `httpd` and `apache2` (and so the guide may well be OK), but for the record:
You need to create a `phabricator.conf` entry under `/etc/apache2/sites-available/` that contains the `<VirtualHost/>` blurb that is in the guide.
Then you need to do something along the following lines:
```
sudo a2dissite 000-default
sudo a2ensite phabricator
sudo service apache2 restart
```
Finally, as an side, the part about `mod_php` being required doesn't seem to be true, at least for `apache2` on Ubuntu.