I'm looking for a charting library written in PHP that outputs to SVG (or Canvas), possibly for integration into an ExtJS project. I like the look of http://pchart.sourceforge.net/index.php but it does bitmap output and is GPL licensed, which will probably be a show-stopper since the project is an internal commercial project.
I highly recommend a PHP + Flotr solution http://solutoire.com/flotr/
Because Flotr is a JS library, all you have to do after your page is loaded is update it on the client-side or run a quick Ajax request back to the server for additional data points.
Here's an example of Flotr pulling JSON data on-the-fly using ajax: http://www.solutoire.com/experiments/flotr/examples/json-data.html
While I prefer Flotr + PHP, there's also a full-featured charting library for PHP that works in roughly the same way, but it's wrapped up as one complete library (JS + PHP): http://phpchart.net