When I now search for keywords I notice that there aren't any php files in the search results.. only htm/html.
There are plenty of PHP files in the results. I have a PHP-only site where the files all have a .php extension, and it shows up just fine. And even if G didn't want to index PHP sites, they really wouldn't be able to block PHP. It's fairly easy to configure another extention to use PHP. For example, you could configure your server to treat all .html files as PHP. And we all know those won't ever be blocked.