This, taken from Google's Fact vs. Fiction page on their site:
Fiction: Sites are not included in Google's index if they use ASP (or some other non-html file-type.)
Fact: At Google, we are able to index most types of pages and files with very few exceptions. File types we are able to index include: pdf, asp, jsp, hdml, shtml, xml, cfm, doc, xls, ppt, rtf, wks, lwp, wri.
While they don't specifically mention php, I know my php pages are included in their search engine. My advice is to create your pages as you normally would, perhaps visit google's Webmaster Guidelines page for helpful tips, and not fret. 🙂
hth
-Elizabeth