Difference: 1. A class can only have one constructor, but can have multiple member methods; 2. If no constructor is written, the system will automatically add a parameterless constructor, but it will not be added automatically. member methods.
The operating environment of this article: Windows 10 system, PHP version 7.1, Dell G3 computer.
The class in php -----class XX{}, through the definition of the class, you can use the member attributes and member methods.
Object---A class is an object. An object can have multiple attributes, and a class can have multiple member methods.
Constructor method: A class can only have one constructor method. The system will have a constructor method function __construct(){} by default. If there are two identical constructors, the previous constructor will be overwritten; If the system has a default constructor and the user defines a constructor, then the user's constructor will be used and the system will ignore the default constructor. In php4, function class name(){} is used to create the constructor, and in php5, __construct(){} is used to create the constructor. The function of the constructor is to initialize the object.
Destruction method: A class can only have one destructor method. If there is no destructor method specified in the class, then the destructor method will not be called (deletion of garbage); the object that enters first will be deleted, and then the destructor method will be deleted. Incoming objects are deleted first. function __destruct(){} cannot pass parameters.
The call of the class does not require the address symbol &, and the content in the class will be automatically called.
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