Not sure the question but for PHP or a dynamic site you need to have it setup where the title, description, and headers all change for each page. They need to be unique! Biggest problem I always see is people leave the title tags the same sitewide.
PHP, HTML, ASP, it doesn't matter it all renders HTML to browsers and search crawlers, PHP is just a power server-side language that can render HTML among many other things. You would still follow the same general SEO practices.
ssandecki is right. To explain further: once the user gets to your .php page, the only thing he is seeing is HTML (and javascript, etc). The same goes for a google spider. Spiders do not care whether your page ends in .html, .php, or anything else. However, make sure your pages do not end in long variable strings, such as index.php?a=16&s=133&x=test ... this will confuse the search engines and negatively affect your ranking. If you have this problem, consider using "rewrite" rules.