How to publish .php page instead of .html at github to demo some php content

I am looking at the following demo – http://blueimp.github.com/jQuery-File-Upload/

To my understanding in the demo, php files are being served from github which means php content can be served / run from github.

I understand the process to publish html content from code hosted at github via this link –
http://help.github.com/pages/

I am just curious to know how can I show a .php page as a demo, similar to what is done in blueimp above.

I tried similar thing at http://synechron.github.com/index2.php
but instead of displaying in the browser window the page gets downloaded in Google chrome and in IE9 index.html is displayed.

Thanks in advance !!