I hope this is right place for this post. I have site with .html pages well indexed in Google. But for the ordering purpose I need .php page. Can I simply add one specific .php page or if I want to have that .php page in my site I need to convert all pages in .php format. I appreciate any advice.
You can simply add php code to your html pages and execute it without changing anything. You will need to add some code to your .htaccess file