Open Source & Web-Based Spreadsheets With PHP – Gelsheet

Gelsheet is a free and open source PHP application for creating web-based spreadsheets.

It is born as a module of Feng Office (OpenGoo) and comes in 3 versions; standalone, WP plugin and Feng Office plugin.

The application offers a desktop-like interface and capable of handling multiple documents with in-cell formulas, styling of content and exporting them to multiple formats.

P.S. Sadly, it lacks of a detailed documentation.