It seems that the only people in favor of making this split, either as a fork, directive or otherwise, are the people that do not intend to switch to this new flavor.
So why not the other way around, with a new flavor named "PHP classic"? Those who do not want to participate in the progression of PHP can opt to run PHP classic instead. - Arnold P.S. I'm not arguing that this, or any split is a good idea. In not even arguing that this is a viable option. Instead, see it as an aid to help you see things from the other side and understand why people are getting emotional.