At times, working within the confines of a Microsoft world can be frustrating, especially when it comes to making more advanced versions of files (i.e. a "real" Excel file versus a CSV). In this example, Justin Silverton gives us an example of how to do just that - use PEAR to create an Excel 5 file.
He uses the Spreadsheet_Excel_Writer package to create the file without the need for getting COM in the mix. The package makes it simple to take in a dataset and write it out to a workbook - complete with column headers.
He shows two ways to save the file as well - creating a local file (on the web server) and pushing it out to the browser.
It's a simple introduction, but it's a starting place - especially for those with a project plan that requires it.