What is the difference between public, private, and protected?

Question

When and why should I use public, private, and protected functions and variables inside a class? What is the difference between them?<

Answer 1

PHP manual has a good read on the question here.

The visibility of a property or method can be defined by prefixing the declaration with the keywords public, protected or private. Class members declared public can be accessed everywhere. Members declared protected can be accessed only within the class itself and by inherited and parent classes. Members declared as private may only be accessed by the class that defines the member.