Interesting, the tooling used in the GitHub actions seems to be a bit out of date. They use 8.4.0RC4 and the composer.phar throws implicit null Notices.

Locally a composer update on the project with 8.4 worked without any issues.

You'll need to ignore platform reqs on 8.4 to get dependencies installed: https://github.com/laminas/laminas-filter/pull/181/files

Thanks for the Tipp. Will check this.

Most risky/truthy Psalm issues can be solved by changing conditionals from if (! $thing) to if ($thing !== null) or $this->thing = $thing ?? 'default', or revert the lockfile and composer update nothing so the psalm issues can be dealt with in a separate patch maybe

This check is failing for a while, but addressing it here would be out of scope and require a separate PR.

PHPUnit for 8.4 latest runs sucessfull now, 8.4 lowest does not.

It seems to be the lowest allowed PHPUnit version. Can we raise it to ^9.6.22 for now? This should fix it.

Yeah - do what you want with dev deps. I always run composer bump -D with abandon.

You may also need to bump laminas-stdlib in require to an 8.4 compatible release because of implicit nulls there.