I understand the way you extend a class like ChildClass extends ParentClass, I understand use of class abstraction and interfaces, and I do understand traits
In the articles I have read most of people stated that traits is used in practice to achieve multiple inheritance that is not done by extends functionality as it supports only single extension.
As I understand traits it is more of a collection of functions that can be used by different classes or other traits.
In this question I ask you to tell me how is it correctly done to literally do extension of more than one class not adding some function-collection.
I can be extremely clear about this:
PHP does not allow this.
I indeed believe that traits provides a way to achieve multiple inheritance, under some restricted conditions. If your codebase is extremely OOP pure and well designed, traits may allow you to achieve multiple inheritence.
But it's not a catch all. If this is a stumbling block for you, don't blame this on PHP's design, you probably need to think about a different way to do what you want. (for example: delegate instead of sub-class).