What are the similarities and differences between interfaces and abstract classes in PHP

The similarities between interfaces and abstract classes:

1. Both abstract classes and interfaces have abstract methods

2. Abstract classes and interfaces cannot create instance objects

3. Abstract classes and interfaces have the same meaning (define a specification)

The difference between interfaces and abstract classes:

1. All methods in the interface must be abstract methods (non-abstract methods cannot be used), so do not use abstract in all methods of the interface, and directly end with a semicolon

2. Member attributes in the interface must be constants (cannot have variables)

3. All permissions of the interface must be public (public)

4 , do not use class to declare the interface, use interface

interface Person{
 public $name; //不能声明变量 报错
  const NAME='tom'// 可以声明常量
 function test();  //因为接口中全部是抽象方法 所以 省去 abstract 。
 function test1();
Protect function test3() 报错 只可以是 public
}
$re=new Person; //报错 不可以 创建实例化 对象 。
echo Person:: NAME; 输出常量。

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