Then they have a couple options: fork and keep their own fork, they can pay the PHP community (or someone in it) to change it back (or to provide a backwards-compatibility mechanism) or pay developers to change their software to work with newer versions of PHP.

They can't bully their way like they tried.

> they can pay the PHP community (or someone in it) to change it back

The decision was defended on its own merit, so I would be really disappointed if bringing money to the table affected the outcome. Funding open source development is great as long as meritocracy is maintained. That's why Linus never accepted a job at a company that had a stake in pushing Linux in a certain direction.

If they could prove that the change would create a really huge expenditure and would thus damage the community, I assume a workaround could be reached through the normal democratic decision process. I imagine a config option to restore the original functionality would be a nice solution, but I'd suggest the company should fund its development (along with proper tests and associated code).

If they kept config files to control every altered behaviour PHP configuration would be an even bigger mess than it is already.