[PHP] 理解依赖注入容器

//简单容器类
class Container {
    private $s=array();
    function __set($k, $c) { $this->s[$k]=$c; }
    function __get($k) { return $this->s[$k]($this); }
}

class User{
    private $c;
    public function __construct(Container $c)
    {
        $this->c=$c;
    }
    public function doBook(){
        $this->c->book->toDo();
    }
    public function doGoods(){
        $this->c->goods->toDo();
    }
}
class Book{
    public function toDo(){
        echo "do book\n";
    }
}
class Goods{
    public function toDo(){
        echo "do goods\n";
    }
}
$c=new Container();
$c->book=function(){
  return new Book();
};
$c->goods=function(){
    return new Goods();
};
$user=new User($c);
$user->doBook();
$user->doGoods();