In a class, a method without a method body is an abstract method. Abstract Visibility Function Method name (parameter 1,.....); If visibility is not specified, the default is public, such as public function Hello ($args), and abstract function work (); Modifier abstract, can also omit
abstract class class name {Properties Method abstract method;}
features of abstract classes:
Abstract classes cannot be instantiated and can only be inherited.
- Abstract classes do not necessarily have abstract methods, classes with abstract methods, must be abstract classes.
- The visibility of an abstract method cannot be private
- Abstract methods in subclasses, need to be overridden.
When do I need to use abstract classes?
- There is a method, the method body does not know how to write, subclasses must also have this method, encapsulated into an abstract method, the class is an abstract class.
- You can use abstract methods when you must encapsulate certain methods in a control subclass.
- When the required control class can only be inherited and cannot be instantiated.
Example: Declaring a human, there is an abstract way to work. Declare a PHP instructor class and rewrite the method to work. Abstract class people{protected $age = 22; Public $height = 1.70; Abstract function work (); } class Phpteacher extends people{function work () {}}if all methods in a class are abstract and have no member properties, then this class is called an interface (interface).
Interface common{abstract function work (); Abstract function test ($args);}
The function of the interface: Although the class of PHP is single-inheritance, it can be implemented through interfaces to achieve multiple inheritance.
Interface Inheritance (extends):
Interface Inheritance Interface
Interface Interface name extends parent interface nameNote: The inheritance of a class is a single inheritance (only one parent), but the inheritance of the interface is multiple inheritance, and the implementation of the class to the interface is also multi-implemented.
Interface implementation (implements):
- Class implements interface class name implements Interface Name 1, interface Name 2, ...
Inheriting classes implement interfaces at the same time:
- The class inherits the parent class and implements the interface class name extends the parent class name implements interface name
An
interface is a special abstract class that contains only abstract methods and no member properties.
- Class implementation (implements) interface, you must fully implement all the methods in the interface, and class inheritance (extends) abstract classes only need to override the abstract methods that are needed.
- Abstract classes can only be inherited, but interfaces are multi-inheritance, and class-to-interface implementations are also multiple implementations.
The use of abstract methods, abstract classes, and interfaces in PHP
