you don't actually even need any php to do this. You can store all the content in seperate files and "ajax in" those files as needed. PHP could be used to provide the same type of separation: providing different content based upon the url. The php page would basically print the info you needed, as though it were a "normal" webpage, using the queryString to select what content you need.
(2013/5) HTML5:90.2% MOB:14% IE7:0.5% IE8:8.6% IE9:9.8% IE10:10%