GelSheet is a free and open source web spreadsheet that allow users to create, edit and export in many formats your everyday work. It's intended to run either standalone or integrated within another web tool. It was born as a part of Opengoo web office
Web-based spreadsheet-like application written in PHP and uses dynamic and interactive user's interface written in JavaScript with jQuery library. Data based on XML.
PHPEditTable is a class which mimics a simple spreadsheet behaviour. It handles cell formatting as well as math expressions based on cells' addresses parsing. Works with complicated formulas, setting properties on cell/row/column/range/sheet level.