What is the difference between inheriting classes and implementing interfaces in php

The difference between inherited classes and implemented interfaces in PHP: 1. PHP inheritance belongs to single inheritance, which ensures unity, but is not flexible enough. Implementing interfaces is a supplement to single inheritance; 2. Implementing interfaces can be done in different places. Expand the functionality of a certain class without destroying the hierarchical relationship.

The operating environment of this tutorial: Windows 10 system, PHP version 7.1, DELL G3 computer

The difference between inherited classes and implemented interfaces in php

1. Comparison between inheritance and interface implementation:

(1) PHP inheritance belongs to single inheritance, which ensures unity, but is not flexible enough. Implementing interfaces is a supplement to single inheritance;

(2) Implementing interfaces can extend the functionality of a certain class without destroying the class hierarchical relationship.

<?php
  class Monkey {
      public $age;
      public $name;
      public function climbing() {
          echo "猴子会爬树<br/>";
      }
  }
  interface iBirdable {
      public function fly();
  }
  interface iFishable {
      public function swimming();
  }
  class LittleMonkey extends Monkey implements iBirdable,iFishable {
      public function fly() {
          echo "猴子还会飞<br/>";
      }
      public function swimming() {
          echo "猴子也会游泳<br/>";
      }
  }
  $littleMonkey = new LittleMonkey();
  $littleMonkey -> climbing();
  $littleMonkey -> fly();
  $littleMonkey -> swimming();
?>

2. Final keyword:

1. If a class does not want to be inherited by other classes (from a security perspective), it can be modified with final;

2 . If you hope that a certain method cannot be overridden by subclasses (you do not want the method to be overloaded by subclass methods), you can also use final modification.

<?php  
class A{  
    final public function getRate($salary){  
        return $salary*0.08;  
    }  
}  
class B extends A{  
    //不能去覆盖父类的getRate方法.  
    /*public function getRate($sal){ 
        return $sal*0.01; 
    }*/  
}  
        
$b=new B();  
echo $b->getRate(100)."<br/>";  
?>

3. Final cannot modify member variables (properties).

3. const:

1. When an attribute does not want to be modified, you can consider using const to make it a constant. For example, pi cannot be tampered with.

2. Basic syntax:

const constant name = assign initial value;

If you do not assign an initial value, it cannot be tampered with later and it will not have a value.

3. Modifiers cannot be written on constants. They default to public but cannot be written out.

4. Constant names are generally named in all capital letters.

5. Calling syntax:

Used inside the class:

self::constant name or class name::constant name;

in External use of the class:

Interface name::constant;

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