Add a static analysis tool like PHPStan

[acelaya]

Introducing a static analysis tool would allow to have a layer similar to TypeScript's type checking.

PHPStan is a good option, but we would need to make sure it does not detect WordPress core functions as undefined.

[SteelWagstaff]

You might also want to look at Psalm? https://psalm.dev/. There's a WordPress plugin available (originally written by Joe Hoyle from Human Made, now maintained by the core Psalm team) that helps with making sure the tool doesn't freak out about not finding WP core functions as well: https://github.com/psalm/psalm-plugin-wordpress