ECshop中的session机制理解

ECshop中的session机制理解

在网上找了发现都是来之一人之手，也没有用自己的话去解释，这里我就抛砖引玉，发表一下自己的意见，还希望能得到各界人士的指导批评！
    此session机制不需要session_start初始化，这个我一直不太清楚还得专家详解。自认为此种机制是建立在COOKIE基础上的模拟session，先用$GLOBALS['_SESSION'] = array();初始化session，然后在cookie中引入session，如$this->session_id = $_COOKIE[$this->session_name]。



最近在做ECSHOP和UCENTERHOME的二次开发,有幸接触到了ECSHOP的SESSION机制,个人认为这种机制相比PHP自带的 SESSION机制拥有更高的安全性和可移植性,尤其是在做多系统共享SESSION时优势更为明显,因此简单的做了一下的代码分析,如有错误,请留言指 点.
<?php



class cls_session
{
var $db             = NULL;
var $session_table  = '';

var $max_life_time  = 1800; // SESSION 过期时间

var $session_name   = '';
var $session_id     = '';

var $session_expiry = '';
var $session_md5    = '';

var $session_cookie_path   = '/';
var $session_cookie_domain = '';
var $session_cookie_secure = false;

var $_ip   = '';
var $_time = 0;

//PHP5的构造函数,用于创建一个SESSION对象,为了保证对PHP4的兼容,其实是在该函数内部调用了和类同名的函数
function __construct(&$db, $session_table, $session_data_table, $session_name = 'ECS_ID', $session_id = '')
{
$this->cls_session($db, $session_table, $session_data_table, $session_name, $session_id);
}


function cls_session(&$db, $session_table, $session_data_table, $session_name = 'ECS_ID', $session_id = '')
{
//将系统自带的$_SESSION初始化为一个空数组并放进全局函数里
$GLOBALS['_SESSION'] = array();

//根据配置文件设置相关的类属性
if (!empty($GLOBALS['cookie_path']))
{
$this->session_cookie_path = $GLOBALS['cookie_path'];
}
else
{
$this->session_cookie_path = '/';
}

if (!empty($GLOBALS['cookie_domain']))
{
$this->session_cookie_domain = $GLOBALS['cookie_domain'];
}
else
{
$this->session_cookie_domain = '';
}

//这里稍微提一下,如果你使用的是HTTPS连接,那么这里需要设置为true
if (!empty($GLOBALS['cookie_secure']))
{
$this->session_cookie_secure = $GLOBALS['cookie_secure'];
}
else
{
$this->session_cookie_secure = false;
}

$this->session_name       = $session_name;
$this->session_table      = $session_table;
$this->session_data_table = $session_data_table;

$this->db  = &$db;
$this->_ip = real_ip();

//如果先前COOKIE中已经保存了sessionid则将他的值赋给session_id属性
if ($session_id == '' && !empty($_COOKIE[$this->session_name]))
{
$this->session_id = $_COOKIE[$this->session_name];
}
else
{
$this->session_id = $session_id;
}

if ($this->session_id)
{
//如果COOKIE中已经存在session_id,取他的前32位做CRC32位校检保证值的正确性
$tmp_session_id = substr($this->session_id, 0, 32);
if ($this->gen_session_key($tmp_session_id) == substr($this->session_id, 32))
{
$this->session_id = $tmp_session_id;
}
else
{
$this->session_id = '';
}
}

$this->_time = time();

if ($this->session_id)
{
//从数据库中取对应session_id的记录保存到$_SESSION中
$this->load_session();
}
else
{
//如果COOKIE中无值或者没能通过校检则创建一个全新且唯一的session_id
$this->gen_session_id();

//写COOKIE
setcookie($this->session_name, $this->session_id . $this->gen_session_key($this->session_id), 0, $this->session_cookie_path, $this->session_cookie_domain, $this->session_cookie_secure);
}


register_shutdown_function(array(&$this, 'close_session'));
}

//生成一个唯一的session_id
function gen_session_id()
{
$this->session_id = md5(uniqid(mt_rand(), true));

return $this->insert_session();
}

//对COOKIE中的session_id做CRC32校检
function gen_session_key($session_id)
{
static $ip = '';

if ($ip == '')
{
$ip = substr($this->_ip, 0, strrpos($this->_ip, '.'));
}

return sprintf('x', crc32(!empty($_SERVER['HTTP_USER_AGENT']) ? $_SERVER['HTTP_USER_AGENT'] . ROOT_PATH . $ip . $session_id : ROOT_PATH . $ip . $session_id));
}

//如果数据库中对应COOKIE内session_id的记录已经不存在,则创建一条对应的空记录
function insert_session()
{
return $this->db->query('INSERT INTO ' . $this->session_table . " (sesskey, expiry, ip, data) VALUES ('" . $this->session_id . "', '". $this->_time ."', '". $this->_ip ."', 'a:0:{}')");
}

function load_session()
{
//检索对应session_id的记录,如果不存在则创建一条空记录
$session = $this->db->getRow('SELECT userid, adminid, user_name, user_rank, discount, email, data, expiry FROM ' . $this->session_table . " WHERE sesskey = '" . $this->session_id . "'");
if (empty($session))
{
$this->insert_session();

$this->session_expiry = 0;
$this->session_md5    = '40cd750bba9870f18aada2478b24840a';
$GLOBALS['_SESSION']  = array();
}
else
{
//如果在SESSION表中检索到对应数据,且SESSION还没有过期则进行相关赋值操作
if (!empty($session['data']) && $this->_time - $session['expiry'] <= $this->max_life_time)
{
$this->session_expiry = $session['expiry'];
//对记录的值做一个MD5校检,以检测后边SESSION值是否发生变化
$this->session_md5    = md5($session['data']);
//反序列化$session['data']将值存到$_SESSION中
$GLOBALS['_SESSION']  = unserialize($session['data']);
$GLOBALS['_SESSION']['user_id'] = $session['userid'];
$GLOBALS['_SESSION']['admin_id'] = $session['adminid'];
$GLOBALS['_SESSION']['user_name'] = $session['user_name'];
$GLOBALS['_SESSION']['user_rank'] = $session['user_rank'];
$GLOBALS['_SESSION']['discount'] = $session['discount'];
$GLOBALS['_SESSION']['email'] = $session['email'];
}
else
{
//否则说明SESSION值超过255字节,则到SESSION_DATA_TABLE表里边查询值
$session_data = $this->db->getRow('SELECT data, expiry FROM ' . $this->session_data_table . " WHERE sesskey = '" . $this->session_id . "'");
//如果在SESSION_DATA_TABLE表中检索到对应数据,且SESSION还没有过期则进行相关赋值操作
if (!empty($session_data['data']) && $this->_time - $session_data['expiry'] <= $this->max_life_time)
{
$this->session_expiry = $session_data['expiry'];
$this->session_md5    = md5($session_data['data']);
$GLOBALS['_SESSION']  = unserialize($session_data['data']);
$GLOBALS['_SESSION']['user_id'] = $session['userid'];
$GLOBALS['_SESSION']['admin_id'] = $session['adminid'];
$GLOBALS['_SESSION']['user_name'] = $session['user_name'];
$GLOBALS['_SESSION']['user_rank'] = $session['user_rank'];
$GLOBALS['_SESSION']['discount'] = $session['discount'];
$GLOBALS['_SESSION']['email'] = $session['email'];
}
else
{
$this->session_expiry = 0;
$this->session_md5    = '40cd750bba9870f18aada2478b24840a';
$GLOBALS['_SESSION']  = array();
}
}
}
}

function update_session()
{
//取得页面中$_SESSION变量内的值
$adminid = !empty($GLOBALS['_SESSION']['admin_id']) ? intval($GLOBALS['_SESSION']['admin_id']) : 0;
$userid  = !empty($GLOBALS['_SESSION']['user_id'])  ? intval($GLOBALS['_SESSION']['user_id'])  : 0;
$user_name  = !empty($GLOBALS['_SESSION']['user_name'])  ? trim($GLOBALS['_SESSION']['user_name'])  : 0;
$user_rank  = !empty($GLOBALS['_SESSION']['user_rank'])  ? intval($GLOBALS['_SESSION']['user_rank'])  : 0;
$discount  = !empty($GLOBALS['_SESSION']['discount'])  ? round($GLOBALS['_SESSION']['discount'], 2)  : 0;
$email  = !empty($GLOBALS['_SESSION']['email'])  ? trim($GLOBALS['_SESSION']['email'])  : 0;
unset($GLOBALS['_SESSION']['admin_id']);
unset($GLOBALS['_SESSION']['user_id']);
unset($GLOBALS['_SESSION']['user_name']);
unset($GLOBALS['_SESSION']['user_rank']);
unset($GLOBALS['_SESSION']['discount']);
unset($GLOBALS['_SESSION']['email']);

$data        = serialize($GLOBALS['_SESSION']);
$this->_time = time();

//如果页面上SESSION的值没有发生变化并且最后一次SESSION更新时间距离当前时间小于10秒则跳出函数
if ($this->session_md5 == md5($data) && $this->_time < $this->session_expiry + 10)
{
return true;
}

//转义SESSION的值用于安全入库
$data = addslashes($data);


if (isset($data{255}))
{
$this->db->autoReplace($this->session_data_table, array('sesskey' => $this->session_id, 'expiry' => $this->_time, 'data' => $data), array('data' => $data));

$data = '';
}

//更新SESSION个字段的值,主要作用是更新expiry这个字段,以此来判断用户是否处于活动状态
return $this->db->query('UPDATE ' . $this->session_table . " SET expiry = '" . $this->_time . "', ip = '" . $this->_ip . "', userid = '" . $userid . "', adminid = '" . $adminid . "', user_name='" . $user_name . "', user_rank='" . $user_rank . "', discount='" . $discount . "', email='" . $email . "', data = '$data' WHERE sesskey = '" . $this->session_id . "' LIMIT 1");
}

//register_shutdown_function将调用这个函数进行SESSION的更新和删除过期数据的操作
function close_session()
{
$this->update_session();


if (mt_rand(0, 2) == 2)
{
$this->db->query('DELETE FROM ' . $this->session_data_table . ' WHERE expiry < ' . ($this->_time - $this->max_life_time));
}

if ((time() % 2) == 0)
{
return $this->db->query('DELETE FROM ' . $this->session_table . ' WHERE expiry < ' . ($this->_time - $this->max_life_time));
}

return true;
}

function delete_spec_admin_session($adminid)
{
if (!empty($GLOBALS['_SESSION']['admin_id']) && $adminid)
{
return $this->db->query('DELETE FROM ' . $this->session_table . " WHERE adminid = '$adminid'");
}
else
{
return false;
}
}

//清空$_SESSION
function destroy_session()
{
$GLOBALS['_SESSION'] = array();

setcookie($this->session_name, $this->session_id, 1, $this->session_cookie_path, $this->session_cookie_domain, $this->session_cookie_secure);


if (!empty($GLOBALS['ecs']))
{
$this->db->query('DELETE FROM ' . $GLOBALS['ecs']->table('cart') . " WHERE session_id = '$this->session_id'");
}


$this->db->query('DELETE FROM ' . $this->session_data_table . " WHERE sesskey = '" . $this->session_id . "' LIMIT 1");

return $this->db->query('DELETE FROM ' . $this->session_table . " WHERE sesskey = '" . $this->session_id . "' LIMIT 1");
}

function get_session_id()
{
return $this->session_id;
}

//得以于这种优秀的机制,现在统计在线活动用户仅需要这么一个简单的查询
function get_users_count()
{
return $this->db->getOne('SELECT count(*) FROM ' . $this->session_table);
}
}

?>