Updating an Excel sheet through a web page

I have a client who wants to have an excel sheet updated through the web page.

He has a form where there are "20 seats" available to users. Once one person signs up that seat is filled, and the persons name needs to be updated to the excel sheet.

What is the best way to approach this?

Is there a program that can achieve this or will this be a PHP thing?

Thanks for any help!

I don't think PHP can handle XLS out of the box but I'm sure there is a lib somewhere that can add this functionnality.

What I know is that PHP can easily handle CSV files (see http://docs.php.net/manual/en/function.fputcsv.php). CSV can then been handled in Exel pretty much like an XLS...

Didn't you have something else with PHP and Excel a few months back? You need to start running away from the Windows clients. :D

Bottom half of page 2 might help: http://www.theregister.co.uk/2007/12/10/pdf_excel_reports_with_php/

EDIT: Actually, that's the writer. Here's a link to the Excel reader. http://sourceforge.net/docman/display_doc.php?docid=22092&group_id=99160