代码详解php中的ArrayAccess接口

$container->session_storage = function ($c) {
    return new $c['session_storage_class']($c['cookie_name']);
};

$container['session_storage'] = function ($c) {
    return new $c['session_storage_class']($c['cookie_name']);
};

abstract public boolean offsetExists ( mixed $offset ) #检查数据是否存在
abstract public mixed offsetGet ( mixed $offset )      #获取数据
abstract public void offsetSet ( mixed $offset , mixed $value )     #设置数据   
abstract public void offsetUnset ( mixed $offset ) #删除数据

interface ArrayAccess 
boolean offsetExists($index) 
mixed offsetGet($index) 
void offsetSet($index, $newvalue) 
void offsetUnset($index)

<?php 
class UserToSocialSecurity implements ArrayAccess 
{ 
private $db;//一个包含着数据库访问方法的对象 
function offsetExists($name) 
{ 
return
 $this->db->userExists($name); 
} 
function offsetGet($name) 
{ 
return $this->db->getUserId($name); 
} 
function offsetSet($name, $id) 
{ 
$this->db->setUserId($name, $id); 
} 
function offsetUnset($name) 
{ 
$this->db->removeUser($name); 
} 
} 
$userMap = new UserToSocialSecurity(); 
print "John's ID number is " . $userMap['John']; 
?>