Are there any tools we can use to automatically create a backup of file like (php file,css file,asp file) and have an extension name of "index.php.(timestamp)".?This is a common problem for developers or if not common I guess they will like it.
I would probably not recommend using that approach, at all. Mainly because it can be fragile, confusing, inconsistent, among other things.
Why not use source control? That way you have a centralized and easy way to compare and rollback to previous versions of a page/script/style sheet/whatever.
Other benefits include integration with tools for things like deployment, project management, analytics, etc.
There are free and open source SCC options out there like:
If you're scared of the command line, the above options all have a "Tortoise" GUI that you can use:
There are sites that offer free hosting as well:
If you absolutely positively can't use source control and still want to make backup files like you originally asked, certain editors will automatically do this for you as you edit/save a file. I know that jEdit does this, and you can specify the number of backup files to make and where to put them (same directory, or standalone directory).