Add missing private property definitions

[clue]

Spotted via phpstan. Missing property definitions means that PHP
automatically allocates new properties as public properties.

Refs #75 and #135

[WyriHaximus]

This raises a question though, should we include phpstan throughout our packages?

[clue]

This raises a question though, should we include phpstan throughout our packages?

I agree that there is some value in this, but I'm not sure it's worth the effort (build matrix is quite big already). I'm open to discuss this in another issue 👍

[WyriHaximus]

This raises a question though, should we include phpstan throughout our packages?

I agree that there is some value in this, but I'm not sure it's worth the effort (build matrix is quite big already). I'm open to discuss this in another issue

Another issue, or would a PR demonstrating it also be an option 😄

[clue]

This raises a question though, should we include phpstan throughout our packages?

I agree that there is some value in this, but I'm not sure it's worth the effort (build matrix is quite big already). I'm open to discuss this in another issue

Another issue, or would a PR demonstrating it also be an option smile

I would say whatever works best for you (or anybody who feels like contributing) 👍 Besides a new tool for our CI setup, this discussion also involves new contribution guidelines (how to run tests and verify everything is "okay" prior to contributing etc.), evaluate what other Q/A tools may or may not make sense (phan etc.) and whatnot. Don't get me wrong, I'm a huge fan of static analysis (tools) and regularly use this as part of higher level applications, so I'm curious to see how much value it provides in these much lower level implementations.