[PHP] 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

[PHP] Can I fork a PHP thread?

There are occasions when I'd like to execute some long-running task in the background, in response to some user action. It seems that PHP has all the neccesary mechanisms to allow me to do this, but in my perusing of the manuals/FAQ's/digests, etc, I don't see such a facility. For example, I'