If you have read this far lets assume you have a real need to use PHP, but are afraid to lose links from other website's to your pages, or that Google might not index your new pages properly.
There is an easier way than re-naming all of your '.htm' page to '.php'... but still using PHP.
I only wish I had this information earlier as I spent hours renaming all of the pages on some of my websites to '.php' in order to use my Visitor Stats 2 tracking program.
Converting your HTML files to PHP
First, you can simply open up the page you want to use PHP, and run a little test.
Lets open a file called 'index.htm' or something similar. At the very top of the page, before even the <html> tag add this code:
(you can simply cut and past this code into your page using Dreamweaver or Notepad)
Now we have a page ready to test for PHP... lets add the PHP functionality for your HTML pages.
Adding PHP functionality to HTML files
Download this file and upload it to the root directory of your website, then rename it to '.htaccess'
This tells your website server to look for any .htm or .html pages and treat them as if they where a .php page... all without even renaming your pages!
You don't even have to update your links, all of your .html or .html pages should be able to run PHP now.
Testing for PHP
Now upload the 'index.htm' page that you added the PHP code to (see above) to your website, and open up your web browser (such as Internet Explorer or Opera).
Type in the name of the uploaded index.htm page, for example:www.mydomain.com/index.htm
If PHP is running properly, you should see the message "Testing that PHP is running ok... success!".
NOTE: some webservers do not support this functionality.
If you see the message, well done! You now have PHP installed and running on your HTML pages!
Creator of Visitor Stats 2