As web designers/developers, MS Office files are pretty far from our daily lives. We usually don't need to create one and, if needed, there are web apps for that.
However, for web apps that host lots of information, enabling users to import/export the data is a huge time-saver and Excel (XLS, CVS) files are the most popular format for that job.
For standard content, we can always export it as a HTML file but, depending on the audience, providing Word files can be a better option.
If you are a PHP developer, working with MS Office files (Excel, Word and Powerpoint in our case) is so easy with the help of mature libraries out there.
Here are alternatives (both simple and complicated) where you may choose the one that fits the best to your project.
A full-featured PHP library for handling and creating Excel files which can read from many different spreadsheet file formats like Excel (.xls), Excel 2007 (OfficeOpenXML -.xlsx), CSV, Libre/OpenOffice Calc .ods, PDF, HTML, etc.
It has support for setting any meta data of spreadsheets (author, title..), adding worksheets/rows/columns, merging cells, manipulating formulas, formatting and much more.
You may also want to read more about its features here.
This PHP library is simple-yet-powerful and supports both writing + parsing files with Microsoft Excel XML/CSV format.
It accepts getting all the cells in a row or only a single cell (the same goes for the column).
A simple library for only generating Excel files.
It takes a 2-dimensional array and converts the data with a single function.
The library is based on the PHP-Excel mentioned above and can export data to Excel-friendly XML, CSV, or TSV.
There is support for streaming the data to a file or as a download.
A set of PHP classes for dynamically generating Excel XML files.
Besides the initial Excel document, it can create sheets and style the output.
This PHP library is only for parsing and retrieving data from XLS files.
It allows targeting any specific cells, counting number of rows and format the output (alignment, colors, borders, etc.).
A powerful PHP library for creating Word files. Actually, .docx files (Office Open XML) which can be opened by many office programs.
Using the library, we can insert text, text breaks, page breaks, headers/footers, tables, list elements, hyperlinks and format all of them.
A PHP library that makes it possible to create a presentation, add slides to it (including test and images), format them and more.
The presentation can be exported as a PowerPoint 2007 (presentationML) or PHPPowerPoint Serialized Spreadsheet file.