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Inheritance, polymorphism, interface, abstract class, abstract method example tutorial in PHP object-oriented

伊谢尔伦

Jun 29, 2017 am 09:29 AM

phpPolymorphisminherit

This article mainly introduces the object-oriented features of the PHP introductory tutorial, and analyzes the inheritance, polymorphism, interface, ## involved in php object-oriented in combination with examples. #Abstract class and abstract methods, etc. Friends who need it can refer to the following

The examples in this article describe the object-oriented characteristics of PHP. Share it with everyone for your reference, the details are as follows:

Demo1.php

<?php
  header(&#39;Content-Type:text/html; charset=utf-8;&#39;);
  //创建一个电脑类
  class Computer {
    //什么叫做类内，就是创建类的花括号内的范围叫做类内，其他地方则类外。
    //public 是对字段的公有化，这个字段类外即可访问，赋值和取值
    public $_name = &#39;联想&#39;;
  }
  $computer = new Computer();
  $computer -> _name = &#39;Dell&#39;;
  echo $computer->_name;
?>

Demo2.php

<?php
  header(&#39;Content-Type:text/html; charset=utf-8;&#39;);
  class Computer {
    //private 是私有化，即对字段进行封装的操作，类外无法访问，取值和赋值都不能操作
    private $_name = &#39;联想&#39;;
  }
  $computer = new Computer();
  echo $computer->_name;
?>

Demo3.php

<?php
  header(&#39;Content-Type:text/html; charset=utf-8;&#39;);
  class Computer {
    private $_name = &#39;联想&#39;;
    //这个时候我采用一个公共对外的方法来访问私有字段
    //因为私有字段只能在类内访问，而对外的公共方法是类内的。
    //更而公共方法又是公共的，所以类外又可访问。
    public function _run(){
      //字段在类内调用的时候必须是类 -> 字段，而$_name只是一个普通变量而已。
      //字段在类外调用的方法是对象 -> 字段，而类内就必须使用 Computer -> _name
      //但是在本类中，可以使用一个关键字来代替字来代替 Computer ，那就是 $this
      echo $this ->_name;
    }
  }
  $computer = new Computer();
  $computer -> _run();
?>

Demo4.php

<?php
  header ( &#39;Content-Type:text/html; charset=utf-8;&#39; );
  class Computer {
    private $name;
    private $model;
    private $cpu;
    private $keyboard;
    private $show;
    private $zb;
    //必须写个对外的入口，才可以取到
    public function getName() {
      return $this->name;
    }
    //必须写一个对内的入口，对私有字段进行赋值
    public function setName($name) {
      //这里的 $name 只是一个变量而已，参数而已
      //$this->name 才是类的字段
      $this->name = $name;
    }
  }
  $computer = new Computer ();
  echo $computer->getName();
  $computer->setName(&#39;Dell&#39;);
  echo $computer->getName();
?>

Demo5.php

<?php
  header ( &#39;Content-Type:text/html; charset=utf-8;&#39; );
  class Computer {
    private $_name;
    private $_model;
    private $_cpu;
    //当类外的对象直接调用私有字段时，会跟着去检查是否有拦截器，
    //如果直接对 $_name 进行赋值，那么set 方法就会拦截住，就不会报错了。
    //采用拦截器进行赋值和取值
    //赋值
    private function set($_key,$_value){
      //采用$_key = &#39;_name&#39;,那么 $_value = &#39;联想&#39;；
      //$this ->_name = &#39;联想&#39;;
      $this ->$_key = $_value;
    }
    //取值
    private function get($_key){
      return $this -> $_key;
      //如果 $_key = &#39;_name&#39; 那么 $this -> _name;
      //如果 $_key = &#39;_cpu&#39; 那么 $this -> _cpu;
      //如果 $_key = &#39;_model&#39; 那么 $this -> _model;
    }
  }
  $computer = new Computer ();
  $computer->_name = &#39;联想&#39;;
  $computer->_cpu = &#39;四核&#39;;
  $computer->_model = &#39;i7&#39;;
  echo $computer->_name;
  echo $computer->_cpu;
  echo $computer->_model;
?>

Demo6.php

<?php
  header ( &#39;Content-Type:text/html; charset=utf-8;&#39; );
  class Computer {
    private $_name;
    private $_model;
    private $_cpu;
    //set 和 get 方法私有了，还是可以执行，是因为
    //因为目前程序的指针已经在类内了。而类内可以执行封装的方法
    //类内执行私有方法，不会出现任何错误。
    //它只需要间接的拦截就可以了。拦截是在内类执行的。
    //说白了，set() 和 get() 是 PHP 内置的方法，具有一定的特殊性
    private function set($_key, $_value) {
      $this->$_key = $_value;
    }
    private function get($_key) {
      return $this->$_key;
    }
  }
  $computer = new Computer ();
  $computer->_name = &#39;联想&#39;;
  $computer->_cpu = &#39;四核&#39;;
  $computer->_model = &#39;i7&#39;;
  echo $computer->_name;
  echo $computer->_cpu;
  echo $computer->_model;
?>

Demo7.php

<?php
  header ( &#39;Content-Type:text/html; charset=utf-8;&#39; );
  class Computer {
    const NAME = &#39;DELL&#39;;
  }
  //常量的输出方法 类::常量
  echo Computer::NAME;    //DELL
?>

Demo8.php

<?php
  header ( &#39;Content-Type:text/html; charset=utf-8;&#39; );
  class Computer {
    public $_count = 0;
    public function _add(){
      $this -> _count++;  //$_count = $_count+1 $_count++
    }
  }
  //做一个累计的效果
  $computer1 = new Computer();
  $computer1 ->_add();
  $computer1 ->_add();
  $computer1 ->_add();
  echo $computer1 -> _count;
  echo &#39;<br />&#39;;
  $computer2 = new Computer();
  $computer2 ->_add();
  $computer2 ->_add();
  $computer2 ->_add();
  echo $computer2 -> _count;
?>

Demo9.php

<?php
  header ( &#39;Content-Type:text/html; charset=utf-8;&#39; );
  class Computer {
    public static $_count = 0;
    public function _add(){
      //如果是静态成员字段，那么就应该用 self 来调用，而不是 $this
      self::$_count++;
    }
  }
  //做一个累计的效果
  $computer1 = new Computer();
  $computer1 ->_add();
  echo Computer::$_count;
  $computer1 ->_add();
  echo Computer::$_count;
  $computer1 ->_add();
  echo Computer::$_count;
  echo &#39;<br />&#39;;
  $computer2 = new Computer();
  $computer2 ->_add();
  echo Computer::$_count;
  $computer2 ->_add();
  echo Computer::$_count;
  $computer2 ->_add();
  echo Computer::$_count;
?>

Demo10.php

<?php
  header ( &#39;Content-Type:text/html; charset=utf-8;&#39; );
  class Computer {
    public static $_count = 0;
    public static function _add(){
      self::$_count++;
    }
  }
  Computer::_add();
  Computer::_add();
  Computer::_add();
  echo Computer::$_count;
?>

Demo11.php

<?php
  header ( &#39;Content-Type:text/html; charset=utf-8;&#39; );
  class Computer {
  }
  $computer = new Computer();
  echo $computer instanceof Computer;
?>

Demo12.php

<?php
  header ( &#39;Content-Type:text/html; charset=utf-8;&#39; );
  //这是父类，电脑类
  class Computer {
    public $_name = &#39;联想&#39;;
    public function _run(){
      echo &#39;联想在运行!&#39;;
    }
  }
  //子类，笔记本电脑类
  class NoteComputer extends Computer {
  }
  $noteComputer = new NoteComputer();
  echo $noteComputer -> _name;
  $noteComputer -> _run();
?>

Demo13.php

<?php
  header ( &#39;Content-Type:text/html; charset=utf-8;&#39; );
  class Computer {
    public $_name = &#39;联想&#39;;
    public function _run(){
      echo &#39;联想在运行!&#39;;
    }
  }
  class NoteComputer extends Computer {
    //我不需要父类的字段和方法，那么可以采用重写的方法覆盖掉父类的字段和方法
    public $_name = &#39;Dell&#39;;
    public function _run(){
      echo &#39;Dell在运行!&#39;;
    }
  }
  $noteComputer = new NoteComputer();
  echo $noteComputer -> _name;
  $noteComputer -> _run();
?>

Demo14.php

<?php
  header ( &#39;Content-Type:text/html; charset=utf-8;&#39; );
  class Computer {
    //私有化，但是无法被子类继承，这个时候就应该用受保护的修饰符来封装
    protected $_name = &#39;联想&#39;;
    protected function _run(){
      return &#39;联想在运行!&#39;;
    }
  }
  class NoteComputer extends Computer {
    public function getTop() {
      echo $this->_name;
      echo $this->_run();
    }
  }
  $noteComputer = new NoteComputer();
  $noteComputer -> getTop();
?>

Demo15.php

<?php
  header ( &#39;Content-Type:text/html; charset=utf-8;&#39; );
  class Computer {
    public $_name = &#39;联想&#39;;
    public function _run(){
      return &#39;联想在运行!&#39;;
    }
  }
  class NoteComputer extends Computer {
    //我子类已经覆盖了父类的字段和方法，
    //但是我又要调用父类的字段和方法，那怎么办呢?
    public $_name = &#39;Dell&#39;;
    public function _run(){
      echo &#39;Dell在运行!&#39;;
      echo parent :: _run();
    }
  }
  $noteComputer = new NoteComputer();
  echo $noteComputer -> _name;
  $noteComputer -> _run();
  //DellDell在运行!联想在运行!
?>

Demo16.php

<?php
  header ( &#39;Content-Type:text/html; charset=utf-8;&#39; );
  //final 如果加在类前面，表示这个类不能被继承
// final class Computer {
// }
  class Computer {
    //final 如果加在方法前面，表示不能够重写些方法
    final public function _run(){
    }
  }
  class NoteComputer extends Computer {
    public function _run(){
    }
  }
  $noteComputer = new NoteComputer();
?>

Demo17.php

<?php
  header ( &#39;Content-Type:text/html; charset=utf-8;&#39; );
  //创建一个抽象类，只要在 class 前面加上 abstract 就是抽象类了
  //抽象类不能够被实例化，就是创建对象
  //只在类里面有一个抽象方法，那么这个类必须是抽象类，类前面必须加上 abstract
  abstract class Computer {
    public $_name = &#39;联想&#39;;
    //抽象类里创建一个抽象方法
    //抽象方法不能够实现方法体的内容
    abstract public function _run();
    //我在抽象类里能否创建一个普通方法
    public function _run2(){
      echo &#39;我是父类的普通方法&#39;;
    }
  }
  //类不能够实现多继承，只支持单继承。
  //抽象类是给子类用来继承的，实现一种规范和资源的共享
  class NoteComputer extends Computer {
    //抽象类的抽象方法，子类必须重写，不然会报错。
    //抽象类里的普通方法不需要重写，子类会直接继承下来
    public function _run(){
      echo &#39;我是子类的方法&#39;;
    }
  }
  $noteComputer = new NoteComputer();
  $noteComputer -> _run();
  $noteComputer -> _run2();
  echo $noteComputer -> _name;
?>

Demo18.php

<?php
  /*
   * 到底应该用抽象类还是接口呢
   * 如果你要继承多个接口的方法规范，那么就用接口好了。
   * 如果你要共享一个方法体内容，那么就用抽象类。
   * */
  header ( &#39;Content-Type:text/html; charset=utf-8;&#39; );
  //创建一个接口
  //接口也不能被实例化
  //接口是为了规范实现它的子类，以达到统一的目的。也可以共享数据
  interface Computer {
    //成员字段必须是变量
    const NAME = &#39;成员 &#39;;
    //接口里的所有方法都是抽象方法，不能够写方法体
    //并且接口的抽象方法不需要写 abstract
    public function _run();
    public function _run2();
  }
  interface Computer2 {
    public function _run3();
  }
  //子类继承接口的说法，叫做实现，接口可以多实现
  class NoteComputer implements Computer,Computer2 {
    public function _run() {
      echo &#39;我重写了run&#39;;
    }
    public function _run3() {
      echo &#39;我重写了run3&#39;;
    }
    public function _run2() {
      echo &#39;我重写了run2&#39;;
    }
  }
  $noteComputer = new NoteComputer();
  $noteComputer -> _run();
  $noteComputer -> _run2();
  $noteComputer -> _run3();
  echo NoteComputer::NAME;
  //接口 :: 常量
  //echo Computer::NAME;
?>

Demo19.php

<?php
  header ( &#39;Content-Type:text/html; charset=utf-8;&#39; );
  //什么叫做多态，字面意思，多种形态
  //一个动作由不同的人去执行，而产生不同的效果或者效果，即为多态。
  //一个人通过不同的状态去执行同一种动作，形成不同的效果，也可以称作为多态。
  //园丁    剪    修理花草
  //理发师  剪    理发
  //总裁    剪    裁员
  //人   笔记本   运行 win7开机了
  //人   台式机   运行 xp开机了
  //创建一个接口，来规范运行的方法
  interface Computer {
    public function version(); //这个方法表示采用什么电脑
    public function work();   //这台电脑是怎么运行的
  }
  //创建一个笔记本的类实现接口
  class NoteComputer implements Computer {
    public function version() {
      echo &#39;笔记本&#39;;
    }
    public function work() {
      echo &#39;可以便携式运行 win7&#39;;
    }
  }
  //创建一个台式机的类实现接口
  class DesktopComputer implements Computer {
    public function version() {
      echo &#39;台式机&#39;;
    }
    public function work() {
      echo &#39;在工作站运行 XP&#39;;
    }
  }
  //创建一个用户
  class Person {
    //创建一个方法来接受电脑(笔记本电脑，也可以是台式电脑)
    //怎么接受，将他们的对象传进来就 OK 啦。
    public function _run($type) {
      echo &#39;这个人的&#39;;
      $type -> version();
      $type ->work();
    }
  }
  //多态的原理，就是类都写好了，不要去修改它，只要在类外的调用参数的更改
  //而最后的结果也会得到更改，那么这个就是多态。
  //有一个接口，两个类，一个是笔记本的类，一个是台式机的类
  //创建了笔记本
  $noteComputer = new NoteComputer();
  //创建台式机
  $desktopComputer = new DesktopComputer();
  //创建一个人
  $person = new Person();
  //使用电脑
  $person -> _run($noteComputer); //这种传递，叫做对象引用的传递
?>

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