部署ArrayAccess界面，可以使得object像array那样操作。ArrayAccess界面包含四个必须部署的方法

1. offsetExists($offset)
2. offsetGet($offset) -> $object[$offset]
3. offsetSet($offset, $value)
4. offsetUnset($offset)

配置文件

// controller.php
<?php
return [
    'home' => [
        'decorator' => [
            'DesignPattern\Decorator\Template'
        ]
    ]
];

核心类

// Config.php
<?php

namespace imooc;

class Config implements \ArrayAccess
{
    protected $path;
    protected $configs = array();
    function __construct($path)
    {
        $this->path = $path;
    }

    /**
     * Defined by ArrayAccess interface
     * Return a value given it's key e.g. echo $A['title'];
     * @param mixed key (string or integer)
     * @return mixed value
     */
    function offsetGet($offset)
    {
        if(empty($this->configs[$offset]))
        {
            $file_path = $this->path.'/'.$offset.'.php';
            $config = require $file_path;
            $this->configs[$offset] = $config;
        }
        return $this->configs[$offset];
    }
    /**
     * Defined by ArrayAccess interface
     * Set a value given it's key e.g. $A['title'] = 'foo';
     * @param mixed key (string or integer)
     * @param mixed value
     * @return void
     */
    function offsetSet($offset, $value)
    {
        if ( array_key_exists($offset,get_object_vars($this)) ) {
            $this->{$key} = $value;
        }
    }
    /**
     * Defined by ArrayAccess interface
     * Check value exists, given it's key e.g. isset($A['title'])
     * @param mixed key (string or integer)
     * @return boolean
     */
    function offsetExists($offset)
    {
        return array_key_exists($offset,get_object_vars($this));
    }
    /**
     * Defined by ArrayAccess interface
     * Unset a value by it's key e.g. unset($A['title']);
     * @param mixed key (string or integer)
     * @return void
     */
    function offsetUnset($offset)
    {
        if ( array_key_exists($offset,get_object_vars($this)) ) {
            unset($this->{$key});
        }
    }
}

使用处

// index.php
$config = new imooc\Config(__DIR__.'./configs');
var_dump($config['controller']);