Joshua Thijssen has put together a new post with details about garbage collection in PHP and a "nice bug/feature/whatsmathing" he found related to it and its performance.
I was playing around with writing a daemon and if you have any experience writing daemons (in any language), there are a few rules you have to live by. For instance, setting your effective uid and gid to a non-privileged user (in case you needed to do some privileged initialization, like opening a socket on a tcp port < 1024), setting the process as a group leader with posix_setsid(), and redirecting stdio file descriptions. And here something went wrong which took a while to find and fix..
He was creating a daemon and the script would just exit without a warning and not continue running. He narrowed down the issue to a few lines (with fopen and fclose) and went to debug it with strace to really see what was happening. He found some unexpected calls in the stack trace and, after some more digging, finally figured out it was a problem of both scope and cleanup that was resulting in the extra calls.