单例模式

Db.php

<?php
/**
 * Created by PhpStorm.
 * User: brady
 * Date: 2019/4/10
 * Time: 14:00
 */

namespace App;


class Db
{
    private static $instance;

    private function __construct()
    {

    }

    public static function getInstance()
    {
        var_dump(self::$instance);
        if(self::$instance == null){
            self::$instance = new self;
        }
        return self::$instance;
    }

    private function __clone()
    {
        // TODO: Implement __clone() method.
    }
}

　　另外一个文件调用 

require_once 'App/CalssLoader.php';
spl_autoload_register('AppCalssLoader::loader',false);


$db =  AppDb::getInstance();
AppDb::getInstance();
AppDb::getInstance();

　　结果

调用多次，只走了一次实例化

代码地址

 git@github.com:brady-wang/laravel-learn.git