gtalent面试：php中什么是依赖注入？容器什么？

<?php

/**
 * 为了约束我们先定义一个消息接口
 * Interface Message
 */
interface  Message{

  public function seed();
}

/**
 * 有一个发送邮件的类
 * Class SeedEmail
 */
class SeedEmail implements Message
{

    public function seed()
    {

        return  'seed email';

        // TODO: Implement seed() method.
    }

}

/** 
 *新增一个发送短信的类
 * Class SeedSMS
 */
class SeedSMS implements Message
{
    public function seed()
    {
        return 'seed sms';
        // TODO: Implement seed() method.
    }


}
/*
 * 订单产生的时候 需要发送消息
 */
class Order{

    protected $messager = '';

    function __construct(Message $message)
    {
        $this->messager = $message;

    }
    public function seed_msg()
    {
        return $this->messager->seed();
    }
}
//我们需要发送邮件的时候
$message = new SeedEmail();
//将邮件发送对象作为参数传递给Order
$Order = new Order($message);
$Order->seed_msg();


//我们需要发送短信的时候
$message = new SeedSMS();
$Order = new Order($message);
$Order->seed_msg();

<?php
/**
 * 为了约束我们先定义一个消息接口
 * Interface Message
 */
interface  Message{

    public function seed();
}

/**
 * 有一个发送邮件的类
 * Class SeedEmail
 */
class SeedEmail implements Message
{

    public function seed()
    {

        return  'seed email';

        // TODO: Implement seed() method.
    }

}

/**
 *新增一个发送短信的类
 * Class SeedSMS
 */
class SeedSMS implements Message
{
    public function seed()
    {
        return 'seed sms';
        // TODO: Implement seed() method.
    }

}


/**
 * 这是一个简单的服务容器
 * Class Container
 */
class Container
{
    protected $binds;

    protected $instances;

    public function bind($abstract, $concrete)
    {
        if ($concrete instanceof Closure) {
            $this->binds[$abstract] = $concrete;
        } else {
            $this->instances[$abstract] = $concrete;
        }
    }

    public function make($abstract, $parameters = [])
    {
        if (isset($this->instances[$abstract])) {
            return $this->instances[$abstract];
        }

        array_unshift($parameters, $this);

        return call_user_func_array($this->binds[$abstract], $parameters);
    }
}

//创建一个消息工厂
$message = new  Container();
//将发送短信注册绑定到工厂里面
$message->bind('SMS',function (){
     return   new  SeedSMS();
});
//将发送邮件注册绑定到工厂
$message->bind('EMAIL',function (){
   return new  SeedEmail();
});
//需要发送短信的时候
$SMS  = $message->make('SMS');
$SMS->seed();

$sms = new  SeedSMS();
$message->bind('SMS',$sms);