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.