If you’ve ever needed to automatically read or generate Excel spreadsheets in PHP, there’s a fantastic library called PHPExcel which will help you with these tasks. It supports Excel 2007 files, is free software (LGPL) and doesn’t require too much memory.
I’ve been using PHPExcel for several months on a commercial project and it has saved me a huge amount of time, as well as giving me the ability to meet client requests for reports which are too complicated to express as CSV files.