I want to introduce to you guys PHPReports (http://phpreports.sourceforge.net), a easy way to make reports on the browser window, using XML, XSLT and PHP.
Its very easy to configure, it uses the Sablotron lib to make the XSL transformation and convert a XML report layout file to PHP code that runs and show your report.
There's some cool features like headers, footers, groups, grouping functions (sum(),max(),min(),avg()...), CSS styles etc etc.