Books.
Do you guys know a good book for professional PHP 7 programming, especially OOP, concepts, design patterns, abstraction, algorithms, security and data structures?
Please not that beginner stuff, I want to dive deeper into PHP 7 😁
Maybe in German or English 😋

Tactical pin

Generally I probably would suggest taking a look how things are done in Symfony 4.

When I started to work with PHP people just started using PHP 5 and I just kind of went with it, improved mostly through guiding of coworkers, PHP 7 isn't such a big change IMO, if you used PHP 5.5/5.6 before. In general for OOP conceps I'd have a look at Java books as they are usually quite well written and concepts can be applied independent of languages.

Thanks for your suggestions @Wack

The reason why I want to improve my knowledge is that I want to do greater things in Symfony 4 😁

That's why I wrote this.

I started to learn / use Symfony from Dec '17 till now and I'm at my third little project now.

Do you have any good point where one can find good examples of how things are done in Symfony 4 except the official documentation?

The last problem I was facing with were abstract classes, which I didn't used before.

I'm not 100% happy with this, but then it's not that bad either: https://codewars.com/collections/... after solving the katas also take a look at voted best practice/discussions.