Stack trace function would be really useful!

Back in my rough-and-ready PHP days, I used to report runtime errors using include("some long description of the error");, which would report: file "some long description of the error" not found in foo.php line 32. Which is great for developers, but awful if a Real User ever sees it. So, lately I've been using a function, handleException(String errorType), which draws a nice page describing gently that something has gone wrong, etc. Unfortunately this way can't report the line number of the function that called it and I'd rather not have to manually include that info at each calling site. If there was a PHP function that printed out the call-stack, I'd be totally set. Is there such a function (I looked, but perhaps with the wrong keywords), or if not, could it be easily added? thanks, dylan