PHP Debug is single API for tracing PHP applications. With a single file of only 200 lines, you can add, with minimal impact, diagnostics to be displayed upon program termination. Each diagnostic contains file, function, and caller function information. You just need to include the debug.php file and add debug() calls throughout your code in the same way as var_dump(). The diagnostic messages are stored and displayed in a list. Diagnostics can be disabled and controlled. It's small and simple yet very versatile.
This is just to document it somewhere... After every new release submission here, the archive is downloaded by BOTs -- I imagine it is not just this one but all Freecode hosted archives (or perhaps those in certain categories). It is easy to distinguish between human and bot, these bots just get the archive and make no other requests. The IP address is different each time. There is one repeated user agent, and one slightly varying user agent. It sure is weird.
The next release will have (the start of) a really cool thing: The comment HTML form will be "designable" by data, not by the code, which means that if someone wanted to add a FORM input, only some data would be changed, not the code.
This is the start of a significant advance, which means that, ultimately, upgrading the code will not undo any modifications a user may have implemented.
This is not plugin type stuff, but simply data -- INI/JSON/XML or whatever we decide to support -- will be all that is needed to customize the code.