[cd34]

IF google prefers .html over .php, yes, that would allow it. There are other factors to keep in mind -- moving existing, indexed content will surely cause an upheaval. Link trades pointed at those .php files will of course get redirects to the .html version which may lose some incoming link influence. You certainly wouldn't want to serve the same page as .php and .html or google may see it as duplicate content and toss one into supplemental (hopefully not the page you're trying to push). I wouldn't really recommend changing existing content, but, for new content I tend to prefer .html. I can see some of the reasoning behind it, but, that is just a tiny factor that I feel has a tiny influence on things.

php parsing itself has a detrimental side effect of setting the last-modified-time of the document to the current time. Technically that is true since the page was composed right then, but, that means that your documents never age and therefore might affect another metric that google looks at. Do you trust a page that is always updated more than a page that is a steady, archival version of an article?

Some of the history behind the different file extensions is a little odd. Ages ago, CPUs weren't as powerful, the php module built into apache wasn't a great performer. You had SSI which allowed you to put things like dates and do simple includes into documents - simplifying menus/navigation.

So, to preserve 'hardware', .html was for a document that needed no parsing, .shtml was used for documents with SSI. .php and .phtml was used for documents that needed php parsing. Because the default server config for .html usually didn't include php parsing, most developers just used .php because it was guaranteed to be parsed.

I could be completely wrong.