I see far too many people trying to improve their execution speed when they have no business doing so.
The node that prompted my posting the Rules of Optimization Club was this one (Print Vs Return In a Subroutine) where the writer wanted to know if it was faster to use print or return. If he wants real speed, he can call exit, too.
The PHP world especially seems to be filled with people who worry about whether it's faster to use interpolation or concatenation to build strings, while tweaking a program that makes SQL queries against unindexed tables and returns the results over the Internet.
It is for these people that the Rules of Optimization Club are most intended.