Permissions on uploaded image don't allow for over writing

PHP List, The Situation: I am building a content management system where users can, among other things, upload images into a directory. The Problem: The image uploads fine, but once it's there, it can't be over written. So if a user uploads an image, and then changes his or her mind and wants to upload a new version over it, the file upload fails. What I've Tried So far: I can manually edit the file permissions using chmod and setting the files to 777. But of course that's not something I want to have to do every time someone uploads a file. I don't know enough about file permissions and settings to know how I can set these permissions at the time that someone makes the upload. The Question: How do I allow a user, who is uploading via the web, place an image on the server with permissions that allow the file to be over written? -- Dave Gutteridge dave@tokyocomedy.com