One of the things I really enjoyed about the CakePHP online API documentation is that for each method and property, you could click a link next to each that would take you to a page containing the source code for the relevant class file and then it would jump down to the first line where the particular item is declared.
Having something like this available would be a tremendous help, since I have been using the online API docs quite a bit. Some times I will see a class constant or something else referenced that isn’t shown in the API docs and can’t easily find where it is declared. If the above feature was implemented, I could simply click one of the links to open the file, look at the top of the source file, and if it’s not there try the next class in the inheritance tree.
Even if class constants were added to the online API docs, it’d still be nice to have links to the method/property declaration to quickly see how something is implemented and/or defined in a particular class.