The new OS X fails to disappoint with new quirks and bugs that I trust Apple will iron out in good time. A few people have shared their problems with pfctl and how its port forwarding no longer works with 10.11. I added some more tips to the AMP -> OS X page on this site for people trying to get homebrew’s httpd to work right. If you can’t find a way to forward ports, you can always just run the program in privileged mode, which gives you a lot more freedom in the end and is really the better setup for testing, if you ask me.