What are code smells in PHP? OOP approach for cleaner code

Many programmers gain too much confidence about their code very quickly with the argument “This is how I do it”. And they feel well ignoring the risks. My approach is to follow as many objective rules and best practices as possible. Programming has been improved for decades and there are many great proven concepts. We save ourselves a lot of time learning them before typing our first line of code. Actually, just a few basic OOP rules help us write significantly better (safer) code — google for SOLID, DRY, SoC, Patterns, Antipatterns. That would be a great starting line for you.