PHP编写一个限制实例化次数的类

实现思路

1. 定义一个static变量$count，用于保存实例化对象的个数
2. 定义一个static方法create，通过该方法判断$count的值，进而判断是否进一步实例化对象。
3. 定义构造函数，$count+1
4. 定义析构函数，$count-1

实现代码

<?php class demo{ public $name; public static $count=0; private function __construct($name){ echo "create $name <br/>"; $this->name = $name; self::$count++; } public function __destruct(){ echo "destory ".$this->name."<br/>"; self::$count--; } public static function create($name){ if(self::$count>2){ die("you can only create at most 2 objects."); }else{ return new self($name); } } } $one = demo::create("one"); $two = demo::create("two"); $two = null; $three = demo::create("three");