well to be honest with u.. i havent learned php yet. i'm starting to learn it. however i like xhtml because with the help of css you can do wonders and not to mention it makes the site faster to load. for example before we had to use javascript to use the rollover effect but now with css its much faster.
you know, i think that not a lot peple tried xhtml (for example me) and can't say what is better, php+html or xhtml. But i know one, all languages are good, so just create pages using your favourite one, and will be ok