PHP object-oriented (interface) basic concepts and abstract class examples introduction

What is an interface (interface)?

Interface is the abstraction of methods. If different classes have the same methods, then you should consider using interfaces.
(1) An interface is a behavioral specification and protocol. In fact, it is an agreement and a constraint between classes. (2) C# does not support multiple inheritance, but it leaves this function to the interface for implementation.
(3) The system resource calling methods between classes are different, making communication between them difficult, but the interface can shield the differences between them and enable them to communicate smoothly.

abstract class(abstractclass)?

constructors. An abstract class can have both abstract methods and concrete methods. An abstract class will not have instances, and these constructors cannot be called by clients to create instances. The constructor of an abstract class can be called by its subclasses, so that all subclasses of an abstract class can have some common implementations, and different subclasses can have their own implementations based on this.

position) instead of inheritance to achieve reuse. 3) Use the template method mode

A class can only inherit one abstract class. . .

Animals must have breathing methods. How to breathe is a matter of subclasses.

attributesand behaviors. Generally speaking, interfaces do not consider attributes, only methods, so that subclasses can freely fill in or extend the methods defined by the interface. As the JAVA prince said, the adapter in event is a good one. application. Using a simple example, such as a teacher, we treat it as an abstract class with its own attributes, such as age, education level, teacher number, etc., and teachers are also divided into many types, we can Inherit the teacher class and extend the unique category attributes, while the universal attributes have been directly inherited.
As for the interface~ Let’s take teachers as an example. Teachers have many behaviors. In addition to the same behaviors as ordinary people, there are also career-related behaviors, such as correcting test papers, giving lectures, etc. We define these behaviors as bodyless. Methods, as a collection, are an interface. Teachers Zhang San and Li Si have different behavioral characteristics, so they can expand their behavioral bodies. In this sense, interface focuses on behavior.
In short, in many cases, interfaces can indeed replace abstract classes, if you do not need to deliberately express inheritance on properties.

The interface defines the general specification for implementing a certain service, declaring the required functions and constants, but does not specify how to implement it. The reason why implementation details are not given is because different entities may need to implement public method definitions in different ways. The key is to establish a set of general principles that must be implemented. Only when these principles are met can the interface be said to be implemented.

Class members are not defined in the interface! The definition of class members is completely left to the implementation class.

Inherit more interfaces

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<?php  
interface  a{  
    public function  foo ();  
}  
interface  b{  
    public function  bar ();  
}  
//一个接口类可以继承多个接口  
interface  c  extends  a ,  b{  
    public function  baz ();  
}  
  
class  d  implements  c  
{  
    public function  foo (){  
    }  
    public function  bar (){  
    }  
    public function  baz (){  
    }  
}  
?>

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