Why does the parent interfere with the creation of the child?

Question

PHP

cognitive question: the parent has a protected constructor, the child (at the moment just an empty class) inherits the parent and when called from the registry, we get an error stating that the protected constructor of the parent is used in the context (of the child, as I understand it)
why the protected constructor of the parent interferes with the creation of the child, if there is no parent in the child?
ps and why child but not son? :)