A notice is not an error. Notices are meant to point out things you may or may not want to investigate.

In this case, you declared a base class that had private variables. Private variables and methods are only visible to objects of that class.

When you derive from a base class, you want the variables to be declared as protected, and the methods to be protected or public.

A notice is not an error. Notices are meant to point out things you may or may not want to investigate.

In this case, you declared a base class that had private variables. Private variables and methods are only visible to objects of that class.

When you derive from a base class, you want the variables to be declared as either private or protected, and the methods to be protected or public, however your mistake was trying to access a private variable directly in the derived class. You should have instead used $obj->getSalary() inside your child method.

A notice is not an error. Notices are meant to point out things you may or may not want to investigate.

A notice is not an error. Notices are meant to point out things you may or may not want to investigate.

In this case, you declared a base class that had private variables. Private variables and methods are only visible to objects of that class.

When you derive from a base class, you want the variables to be declared as protected, and the methods to be protected or public.