I want to write a PHP script to update my rss feed whenever there is a change or nightly if the above is to hard, but I don't know how. Any guidance?

Are you using a database? Instead of a static feed (a file) you can use a PHP script to generate it. It will always be up-to-date then.

Right now the data I'm storing is flat file because I've heard mysql isn't as good at storing images and there are sql injection security vulnerabilities, which I don't know how to safe guard against. I take it you mean write a PHP to draw from a DB and then output an RSS. That would be more elegant than my flat file approach, and if I knew how to work around those concerns, I would want to implement it.

Wouldn't matter, reading from a flat file should work too.