Simple example of static variables in PHP object-oriented programming

Let me introduce to you an example of static variables in PHP object-oriented programming. Friends in need can refer to it.

As for what PHP object-oriented static variables are, they have been introduced a lot in previous PHP tutorials. You can review them.

Let’s look at today’s problem. There is a group of friends playing a hide-and-seek game. New children join from time to time. How do you know how many people are playing now? Please use object-oriented thinking and write a program to solve the problem.

There are two ways to solve this problem: use global variables and static variables.

<?php
    //有一群朋友在玩捉迷藏游戏,不时有新的小朋友加入,
    //请问如何知道现在共有多少人在玩?
    //请使用面向对象的思想，编写程序解决。
/*
    //1种方法使用全局变量
    
    global $global_nums;
    //先声明全局变量后再对它进行赋值
    $global_nums=0;

    class Child{
    
        public $name;
        
        //构造方法
        public function __construct($name){
            
            $this->name=$name;
        }

        //定义一个方法统计人数
        public function allPlay(){
            //先声明使用全局变量
            global $global_nums;
            $global_nums+=1;
            echo $this->name."加入游戏.<br/>";
        }
    }

    $p1=new Child("lily");
    $p1->allPlay();
    $p2=new Child("lucy");
    $p2->allPlay();
    $p3=new Child("kucy");
    $p3->allPlay();
    echo $global_nums;
    //by bbs.it-home.org
*/
  //第二在类中 使用静态变量
    class Child{        
        public $name;
        //在类中声明静态变量
        public static $allPlay=0;
    
        public function __construct($name){
            
            $this->name=$name;
        }
        
        //统计人数
        public function addPlay(){
            //在类中使用静态变量。在类中有下面2中方式访问静态变量
            //self::$静态变量名和类名::$静态变量名
            //self::$allPlay+=1;
            Child::$allPlay+=1;
            echo $this->name."加入游戏.<br/>";

        }
    }

    $p1=new Child("lily");
    $p1->addPlay();
    $p2=new Child("lucy");
    $p2->addPlay();
    $p3=new Child("kucy");
    $p3->addPlay();
    $p4=new Child("uucy");
    $p4->addPlay();

    //在类外只有一种方式访问静态变量：类名::$静态变量名
    echo Child::$allPlay;
?>