PHP learning 2 -- classes and objects

Class and Object
1. stdclass cannot be defined

2. in PHP, _ hitting is regarded as a magic function, __sleep and _ wakeup are magic functions in the PHP class and cannot be named, we recommend that you do not start the function name with _ in PHP. *****

3. Define and use a class similar to the class in C ++, and reference the class pointer in the member, plus $ **

4. class inheritance can only be single inheritance, and the sequence is inherited ***

5. the constructor first finds a function with the same name as the class, and does not call the upper-level constructor successively ***

6. The parent class name can be replaced by parent. The class inheritance overwrites the class name ,**

7. The member functions of the class have no object restrictions. They can be used as external functions directly: The role calls *****