接“秒杀系列04”上文：

主要更改的文件有：

Dsn.php

<?php
namespace App\test;
class Dsn {
    private $dsn = "mysql:host=192.168.0.101;dbname=seckill;charset=utf8;user=seckill;password=BBHyiFWiXrpxji5S;";
    public function getdsn() {
        return $this->dsn;
    }
}

Db.php

<?php
namespace App\test;

use PDO;

class Db {
    private $pdo;
    public function __construct($dsn) {
        try {
            $this->pdo = new PDO($dsn);
            $this->pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
        } catch (PDOException $e) {
            echo "mysql连接失败:" . $e->getMessage();
        }
    }

    public function queryForRows($sql) {
        try {
            $stmt = $this->pdo->query($sql);
            return $stmt->fetchAll(PDO::FETCH_ASSOC);
        } catch (PDOException $e) {
            echo "查询失败:" . $e->getMessage();
        }
    }
}

User.php

<?php

namespace App\test;

class User {
    private $db;

    public function __construct(Db $Db)   // 这里直接注入Db的实例了
    {
        $this->db = $Db;  // 这里不在主动实例化Db了，直接用注入的Db实例
    }

    public function getAllUsers() : array {
        return $this->db->queryForRows("select * from users");
    }
}

beans.php

<?php
namespace App\test;

use DI\Container;

return [
    Dsn::class => function() {
        return new Dsn();
    },

    Db::class => function(Container $c) {
        return new Db($c->get(Dsn::class)->getdsn());
    },

    User::class => function(Container $c) {
        return new User($c->get(Db::class));
    }
];