File Editing and Permissions

[eluser]Eric Cope[/eluser]
I am creating an install script that needs to edit CI config files. Below are the steps
1) User FTPs all files to server
2) User browses to install script and enters all user data
3) PHP script edits CI config files, updates database, deletes install files

I want to automate 2 and 3. the problem is that the files are uploaded using the user's account, not Apache's. To edit the files, Apache needs r+w access.

Any ideas, other than granting write access to the world?