php-export-data by Eli Dickinson
Released under the permissive MIT License: http://www.opensource.org/licenses/mit-license.php
A simple library for exporting tabular data to Excel-friendly XML, CSV, or TSV. It supports streaming exported data to a file or directly to the browser as a download so it is suitable for exporting large datasets (you won't run out of memory).
Excel XML code is based on Excel_XML by Oliver Schwarz (http://github.com/oliverschwarz/php-excel)
How to use it
// When executed in a browser, this script will prompt for download
// of 'test.xls' which can then be opened by Excel or OpenOffice.
// 'browser' tells the library to stream the data directly to the browser.
// other options are 'file' or 'string'
// 'test.xls' is the filename that the browser will use when attempting to
// save the download
$exporter = new ExportDataExcel('browser', 'test.xls');
$exporter->initialize(); // starts streaming data to web browser
// pass addRow() an array and it converts it to Excel XML format and sends
// it to the browser
$exporter->addRow(array("This", "is", "a", "test"));
$exporter->addRow(array(1, 2, 3, "123-456-7890"));
// doesn't care how many columns you give it
$exporter->finalize(); // writes the footer, flushes remaining data to browser.
exit(); // all done
See the test/ directory for more examples.
Some other options for creating Excel files from PHP are listed here: http://stackoverflow.com/questions/3930975/alternative-for-php-excel/3931142#3931142