I'm using a popular PHP script for my web site, which uses main_1.htm for the header and footer, and inner_index.htm for the main part of the home page. Also, of course it has index.php.

How can I set up a duplicates of these files to work on and test changes to the home page, before I actually deploy the changes on to my live site's home page?

Thanks

Ideally you have to make full site copy at local server and implement changes there. As soon changes done, you may to upload it to the host server.

Use Aptana or other editor who suport FTP sync. This way you can acomplish more easy the upload & sync. Just edit the file and then when is ready -> upload it