"Impossible!" you cry. "Excel uses some proprietary Microsoft file format. This can't be done!"
Yes, it can. Spreadsheet_Excel_Writer generates the "real thing", complete with Excel functions, formatting and all. No, we're not talking generating comma separated files here, or using the COM extension (or any other extension, for that matter). This is written in pure PHP and will work just as well from a UNIX-based Web server as it does from a Windows-based server -- and there's no need to bug your hosting provider. In short, PEAR::Spreadsheet_Excel_Writer, with additional magic from PEAR::OLE, "understands" Microsofts Excel file formats.