(First of all, if this is intentional then I apologise. It looked to me that this project was no longer being maintained on Source Forge)

While getting this to run I've encountered the following error message:

An unknown PHP error occurred. This is most likely a syntax error in config.php in phpVirtualBox's folder. The most common errors are an unclosed quote or a missing semicolon in a configuration item that has been entered (e.g. location, username, or password).

Depending on your PHP configuration, navigating directly to config.php in your web browser may display the PHP error message.

If find that this is not the case, or have no idea what this error message means, please raise the issue at http://sourceforge.net/p/phpvirtualbox/discussion/help/

In the last paragraph the link points to sourceforge.net. Should that now be github?