Create online PHP form and save results in CSV

I have a website that uses PHPProBid auction software which allows members to Bulk Upload their listings in a CSV file. I would like to create a form with all of the required information for the CSV file. Members should then be able to save their listings in a CSV files for upload to the site. Members should be able to add to their previously saved CSV file and be able to view each CSV listing online (similar to eBay's TurboLister)