what I personally would like to see is a tool that helps me to undererstand the codebase. Maybe a sourcecode visualizer.

When I need to start on new projects with existing codebase I would love a visual map or something of all the components in the source code (before I dive into the sourcecode itself and spend hours or days to understand how everything works together. Personally I need this for php and javascript. I use xdebug profiler for php but thats too much info and I need to run the webapp. I need something that is able to anazyle and visualize the code without executing it.