I just found http://dev.slimframework.com/phpdocs/ (nice!) but I noticed that http://dev.slimframework.com/phpdocs/graph_class.html does not load an image. Maybe this could be fixed as it would be quite a useful resource.
Those documents are very old and shouldn’t be considered valid for Slim 3, assuming from your other posts that you are using version 3.
OK, thanks for the heads-up.