Hi,
Pokki includes a custom version of the Chrome engine browser, so it's an implementation of the "client side web". PHP is a server-side scripting language, and relative to your server.
In Pokki you can develop in JavaScript, wich allows you however, to execute some AJAX Calls to your own PHP Scripts on your server, since we're using a custom Chrome engine you are allow to do Cross Domain XHR.
Cheers,
J.