PHPStan Setup

[askvortsov1]

PHP doesn't give us that much built-in type safety. With PHPStan, we could perform static analysis to confirm:

• Closure typing
• Array shapes
• Typed arrays
• Generics

While this probably won't be 100% ideal (especially when it comes to editor integration), it would be a HUGE step up from where we are now.

[SychO9]

phpstan is a default plugin in phpStorm, but I never noticed closure typings or array shapes before 😬, that's neat.

Yeah, we should definitely have it setup. Perhaps I can start by going through the backend and add closure typings first.

[tankerkiller125]

I'll push my changes on this tonight hopefully so that we can get the list of legit errors we need to fix, and work on building stubs/fixes for any remaining ones.