依赖注入

• 依赖注入主要用来减少代码间的耦合
• 有效分离对象和它所需的外部资源

Order.php

<?php
include('AliPay.php');
include('WechatPay.php');

class Order
{

    public function buy($obj)
    {
        return $obj->pay();
    }
}

$AliPay = new AliPay();
$WechatPay = new WechatPay();
echo (new Order)->buy($AliPay);
echo (new Order)->buy($WechatPay);

AliPay.php

<?php

class AliPay
{
    public function pay()
    {
        return '我是支付宝支付';
    }
}

WechatPay.php

<?php

class WechatPay
{
    public function pay()
    {
        return '我是微信支付';
    }
}