Although the pages are written only in Japanese, I’m sure you will get what they are for.
They are built with Highcharts, probably the very best library for drawing charts. I really love it. It’s incredibly powerful.
Of course in the backend lies yii framework (1.1), with MySQL.
In fact the whole site is built upon yii. (The site is for a local community which I belong. )
I hope I get a chance to play with Highcharts someday.
Is the Highcharts used there an Yii extension, or just js and css?
There’s no extension for it, as far as I know. And I believe that we don’t need that kind of thing at all.
What we have to do with Yii for it is mainly the server side job of providing the chart data which Hightcharts requires for the initial page loading and for the ajax updating.