这是 IoC 吗？

参考 http://weibo.com/p/230418661838ca0102vbhb
http://laravelacademy.org/post/769.html
新手对 Ioc 的理解，不知对不对。

<?php
    class Ioc
    {
        public $arr=[];
        public function set($key,$course)
        {
            $this->arr[$key]=$course;
        }
        public function get($key,$class='')
        {
                return $this->arr[$key]($class);
        }
    }
    class Fac
    {
        public static $ins;
        public static function create($class){
           return self::$ins=$class;
        }
    }
    class Pro1
    {
        function test(){
            echo 'i am Pro1';
        }
        function demo(){
            echo '对象不会被覆盖';
        }
    }
    class Pro2
    {
        function test(){
            echo 'i am Pro2';
        }
    }
    $Fac=function ($class){
        return Fac::create($class);
    };
    $Pro1=function(){
        return new Pro1;
    };
    $Pro2=function(){
        return new Pro2;
    };
    $Ioc=new Ioc;
    $Ioc->set('Fac',$Fac);
    $Ioc->set('Pro1',$Pro1);
    $Ioc->set('Pro2',$Pro2);
    $Pr1=$Ioc->get('Fac',$Ioc->get('Pro1'));
    $Pr2=$Ioc->get('Fac',$Ioc->get('Pro2'));
    $Pr1->test();// i am Pro1
    $Pr2->test();// i am Pro2
    $Pr1->demo();//对象不会被覆盖