In PHP, this includes methods, constants, and fields inside classes. In particular, I should be able to click on `Zerg::rush()` and be linked to the definition of the method `rush()` inside the class `Zerg`, as opposed to either nothing or a list of all functions anywhere named rush(). (And if I click on `$mystery->meat()`, it should find all methods called `meat()`, since it doesn't know what class to look in.) This obviously can be extended to languages other than PHP.
PHP should be working fully now. Not so much for other languages, since the symbol linking JS is annoyingly language-specific. Maybe later if there's time and interest.
(Aside: It would also be nice to do symbol search on the fly, to avoid having to run a cron job, but I don't think that's feasible. We could at least scan the changed files whenever a new commit comes in, and regenerate symbols for those files immediately.)