PHP Object-Oriented programming

1. Basic object-oriented concepts

class: abstraction of the same class of things

objects: Instances of classes

member variables: variables defined inside a class that are not visible to the outside, but can be accessed through member functions, which are called properties of the object after the class is instantiated as an object

　　member functions: defined within a class, which can be used to access the data of an object

　　 member modifier :Public Private protected

Public: Publicly available members, accessible from any location

Private member, accessible only within the class

Protected: A protected member that can be accessed inside the class and within the subclass, not outside the class.

PHP Object-Oriented programming