<?php
class A{
private static $ob=null;
private function __construct(){}
public static function display(){
if(self::$ob == null)
return self::$ob = new A();
else
return self::$ob;
}
}
$a = A::display();
$b = A::display();
var_dump($a);
var_dump($b); 
![[Web-Frontend] Node.js-Schnellstart](https://img.php.cn/upload/course/000/000/067/662b5d34ba7c0227.png)
