I have a question to the PHP-in-production crowd: how long do you wait before migrating to higher version of PHP? Is the first release usually already fine, or is it better to wait for a few months and let someone else catch the early errors?
I wait 1-3 months, but then update. It used to take way longer, because Amazon's Elastic Beanstalk platform would take longer to update, but I've now changed to Platform.sh and the transition should be easier.
It has been very backward-compatible (i.e. stuff that works in 8.n also works in 8.n+1; and unless you use exotic functions or are relying on special functionality, it should work for you, too).
Once I'm at 8.4, I would slowly update the code / syntax with rector and the assistance of phpstan.
For framework updates I wait 1-2 patch versions before updating, because of composer dependency problems and sometimes bugs do still find themselves into new releases (e.g. I would wait at least until Symfony 7.2.1 before upgrading from Symfony 7.1.x).
It also often fit with the current Laravel version (11).
I enjoy the PHP 8 new features such as named arguments, constructor arguments promotion and nullsafe operators. Made my new code a lot more readable.
I am not that sure about 8.4 yet, though the new array_ functions and new DOM look interesting.
Yeah, this is a huge problem, but also, in the long run, inevitable.
Plenty of Kernighan & Ritchie C code still out there...
But K&R C is now so dated, protoize was removed from GCC 4.5 and onwards. When (in a bout of idiosyncrasy) I wanted to convert some ancient K&R C to new style a couple of years back, I ended up putting GCC 4.4 in a Docker container to make it easier: https://github.com/skissane/protoize
We upgrade the development environment around the time when our tooling (phpstan, cs-fixer) runs on the next version, but doesn't necessarily support new language features.
We upgrade the production environment when our tooling supports most of the new language features and at least all of the ones we want to make use of.
This usually happens within 3-6 months of the release. By that time the version has stabilized enough to be safe for production use.
I still have a PHP5 project that somehow still runs.
As long as you do not use the new functionality, I'd claim that a new PHP version is no less stable than an older one. And on a contrary you would be missing out on some bugfixes that were deemed too risky to apply to an existing version.
Disclosure: I've got a commit-bit for PHP, so we had in-house expertise to diagnose issues ourselves.
I guess depending on the app that might not really matter, but that seems like it could be an issue at some point.
The licensing is on the order of thousands or low tens of thousands per year. Worth it for a 40-person business that has a 20-year-old legacy codebase supporting a few million dollars a year revenue. It's not what we think of as a standard "tech" company but it describes an absolutely ridiculous number of businesses.
Also external tooling, like for example NewRelic extension, takes some time to release a version that supports the new release.