[gog]

I am working on a ~10 year old PHP project, the amount of changes that needed to be made in the last decade because of the changes in the language are almost non-existent.

But using new features is nice and makes the code better, there are even projects (rectorphp) that can automate using of new features in the existing codebase.

[motogpjimbo]

The only time I've ever had to update legacy code due to a breaking change in PHP is when an old encryption algorithm was withdrawn and I had to write a migration to decrypt and re-encrypt the data we'd originally encrypted with it. Apart from that (and a few notices sent to Sentry) it's been smooth sailing over the years.