Create small graph from API code

Given a result like this from the getClicky API: [login to view URL] I need a graph created that would fit in the toolbar for a WordPress blog. The result should look like this: [login to view URL] I'd only need the lines, which would become whiter in color as more visitors are shown. The background color should be transparent. The graph should be served as an image. The project needs to be coded in PHP and should work with the minimum requirements for WordPress: [login to view URL]