by Michael(tm) Smith
Related link: http://www.aditus.nu/jpgraph/
The Web-based "Release Planner" interface that I use at my company for editing and viewing data (bug lists, schedules, etc.) for releases of our software lacks one important feature: It can't display Gantt charts of project schedules. So, a while back I went hunting for something I might be able to use to build an app to generate Gantt charts from the data in our release-planning database. After hitting a number of dead-ends, I came across JpGraph and realized right away that it was exactly what I needed.
JpGraph is an PHP-based object-oriented library you can use to generate a variety of graphs/charts: pie charts, bar graphs, polar plots, line plots, error plots, scatter plots, field plots, box/stock/candle charts, radar graphs, ... and Gantt charts. There are some thumbnail examples of various JpGraph-generated images at the JpGraph website. Below is an example of a JpGraph-generated Gantt chart.
JpGraph has a great set of features, is well documented (comes with a how-to guide that runs to about 150 pages), and the source code is clean and easy to work with if you need to make modifications to it. It's a nice piece of work all around.
dotproject uses this
Dotproject (dotproject.net) uses this for all of their gantt chart creation and display.
Check out cacti for great graphs: