What's the best way to create a backup file in a project (not using CVS)?

My current method is to copy a file and rename the copy. Say, from "file.php" to "file.php_". I seem to recall that before v5.0, I was able to do this even with a file open. Something like I would right-click the file, SaveAs, and it would not update in the IDE (unlike Rename). Now, however, both SaveAs and Rename update the file when open in the editor.

In Dreamweaver, I have a right-click "Duplicate" function that produces a "copy of file.php" from "file.php".

Using this method, one thing I have discovered that works is, with the file open and active in IDE, select the file in Workspace, right-click, rename to "file.php_". This updates in the editor. Then, in that file in the editor, choose File>>SaveAs, "file.php". I now have a file.php (active) and file.php_ in my folder.

Is there a better way?

File-SaveAs does not delete the old file, until it is a newly created file. So you can get a file copy.
Rename just changes the file name and therefore it's not suitable for getting file copy.
Also you may want to enable tools->settings->IDE Settings, Create backup files.