CI的Session并不是原生的session，正是我前面所有的cookie based session,另外，CI可以根据用户选择配置是否将session存入数据库中，本人很喜欢这个功能，还有就是“闪出数据”的功能，既闪出数据只是对下次服务器请求可以，之后就会被自动清除。常见使用方法有：

$this->session->set_userdata('some_name', 'some_value'); //设置session数据

$this->session->userdata('item'); //获取session数据

$this->session->unset_userdata('some_name'); //删除session数据

$this->session->sess_destroy(); //销毁session数据

$this->session->set_flashdata('item', 'value'); //设置闪存数据

$this->session->flashdata('item'); //获取闪存数据

$this->session->keep_flashdata('item'); //保留闪存数据

复制代码 代码如下:
/**
* CI是 session based cookie
*/
class CI_Session {
var $sess_encrypt_cookie= FALSE; //是否对session加密
var $sess_use_database= FALSE; //是否将session存入数据库
var $sess_table_name= ''; //session存入数据的表名
var $sess_expiration= 7200; //session的过期时间
var $sess_expire_on_close= FALSE; //当浏览器窗口关闭时是否自动使session过期
var $sess_match_ip= FALSE;//是否通过用户的IP地址来读取 session 的数据
var $sess_match_useragent= TRUE; //是否要按照对应的 User Agent 来读取 session 数据。
var $sess_cookie_name= 'ci_session'; //cookie名称
var $cookie_prefix= ''; //cookie前缀
var $cookie_path= ''; //cookie路径
var $cookie_domain= ''; //cookie作用域
var $cookie_secure= FALSE; //是否在安全的https协议下才有效
var $sess_time_to_update= 300; //session cookie多久更新一次
var $encryption_key= ''; //加密key
var $flashdata_key= 'flash';
var $time_reference= 'time';
var $gc_probability= 5; //回收session的能力
var $userdata= array(); //用户session数据保存变量
var $CI; //CI超级句柄
var $now; //当前时间
public function __construct($params = array())
{
log_message('debug', "Session Class Initialized");
// 获取CI超级类
$this->CI =& get_instance();
// 获取config文件中的配置数据
foreach (array('sess_encrypt_cookie', 'sess_use_database', 'sess_table_name', 'sess_expiration', 'sess_expire_on_close', 'sess_match_ip', 'sess_match_useragent', 'sess_cookie_name', 'cookie_path', 'cookie_domain', 'cookie_secure', 'sess_time_to_update', 'time_reference', 'cookie_prefix', 'encryption_key') as $key)
{
$this->$key = (isset($params[$key])) ? $params[$key] : $this->CI->config->item($key);
}
//必须设置encryption_key
if ($this->encryption_key == '')
{
show_error('In order to use the Session class you are required to set an encryption key in your config file.');
}
// 加载string helper函数
$this->CI->load->helper('string');
// D如果对cookie进行加密，则引入加密类
if ($this->sess_encrypt_cookie == TRUE)
{
$this->CI->load->library('encrypt');
}
// 如果session计入数据库，则引入db
if ($this->sess_use_database === TRUE AND $this->sess_table_name != '')
{
$this->CI->load->database();
}
// 获取当前时间
$this->now = $this->_get_time();
// 如果没有设置session的有效时间，默认两年
if ($this->sess_expiration == 0)
{
$this->sess_expiration = (60*60*24*365*2);
}
// 获取cookie名称
$this->sess_cookie_name = $this->cookie_prefix.$this->sess_cookie_name;
// 如果session不存在，创建新会话
if ( ! $this->sess_read())
{
$this->sess_create();
}
else
{
$this->sess_update();
}
// 闪出标记old的闪出数据
$this->_flashdata_sweep();
//将新的闪出数据标记成old 标记成old的数据的数据将会在下次请求时闪出
$this->_flashdata_mark();
//回收/删除 过期的session
$this->_sess_gc();
log_message('debug', "Session routines successfully run");
}
// --------------------------------------------------------------------
/**
* 读取session数据
*/
function sess_read()
{
// 获取session
$session = $this->CI->input->cookie($this->sess_cookie_name);
// 没有session 拜拜
if ($session === FALSE)
{
log_message('debug', 'A session cookie was not found.');
return FALSE;
}
// 如果加密了cookie
if ($this->sess_encrypt_cookie == TRUE)
{
$session = $this->CI->encrypt->decode($session);
}
else
{
// encryption was not used, so we need to check the md5 hash
$hash = substr($session, strlen($session)-32); // get last 32 chars
$session = substr($session, 0, strlen($session)-32);
// Does the md5 hash match? This is to prevent manipulation of session data in userspace
if ($hash !== md5($session.$this->encryption_key))
{
log_message('error', 'The session cookie data did not match what was expected. This could be a possible hacking attempt.');
$this->sess_destroy();
return FALSE;
}
}
// 反序列化存入cookie的session数组
$session = $this->_unserialize($session);
// 检测session的数据
if ( ! is_array($session) OR ! isset($session['session_id']) OR ! isset($session['ip_address']) OR ! isset($session['user_agent']) OR ! isset($session['last_activity']))
{
$this->sess_destroy();
return FALSE;
}
// session数据过期了吗
if (($session['last_activity'] + $this->sess_expiration) < $this->now)
{
$this->sess_destroy();
return FALSE;
}
// 是否是根据用户ip来读取session数据
if ($this->sess_match_ip == TRUE AND $session['ip_address'] != $this->CI->input->ip_address())
{
$this->sess_destroy();
return FALSE;
}
// 是否根据ua来匹配session数据
if ($this->sess_match_useragent == TRUE AND trim($session['user_agent']) != trim(substr($this->CI->input->user_agent(), 0, 120)))
{
$this->sess_destroy();
return FALSE;
}
// 如果session入库了，这种方式应该更安全点，当然负载大时，就不建议了，数据库读写压力大
if ($this->sess_use_database === TRUE)
{
$this->CI->db->where('session_id', $session['session_id']);
if ($this->sess_match_ip == TRUE)
{
$this->CI->db->where('ip_address', $session['ip_address']);
}
if ($this->sess_match_useragent == TRUE)
{
$this->CI->db->where('user_agent', $session['user_agent']);
}
$query = $this->CI->db->get($this->sess_table_name);
// No result? Kill it!
if ($query->num_rows() == 0)
{
$this->sess_destroy();
return FALSE;
}
// Is there custom data? If so, add it to the main session array
$row = $query->row();
if (isset($row->user_data) AND $row->user_data != '')
{
$custom_data = $this->_unserialize($row->user_data);
if (is_array($custom_data))
{
foreach ($custom_data as $key => $val)
{
$session[$key] = $val;
}
}
}
}
// Session is valid!
$this->userdata = $session;
unset($session);
return TRUE;
}
// --------------------------------------------------------------------
/**
* 将读取的session数据写入
*/
function sess_write()
{
// 是否写入db
if ($this->sess_use_database === FALSE)
{
$this->_set_cookie();
return;
}
// set the custom userdata, the session data we will set in a second
$custom_userdata = $this->userdata;
$cookie_userdata = array();
// Before continuing, we need to determine if there is any custom data to deal with.
// Let's determine this by removing the default indexes to see if there's anything left in the array
// and set the session data while we're at it
foreach (array('session_id','ip_address','user_agent','last_activity') as $val)
{
unset($custom_userdata[$val]);
$cookie_userdata[$val] = $this->userdata[$val];
}
// Did we find any custom data? If not, we turn the empty array into a string
// since there's no reason to serialize and store an empty array in the DB
if (count($custom_userdata) === 0)
{
$custom_userdata = '';
}
else
{
// Serialize the custom data array so we can store it
$custom_userdata = $this->_serialize($custom_userdata);
}
// 更新session记录
$this->CI->db->where('session_id', $this->userdata['session_id']);
$this->CI->db->update($this->sess_table_name, array('last_activity' => $this->userdata['last_activity'], 'user_data' => $custom_userdata));
// Write the cookie. Notice that we manually pass the cookie data array to the
// _set_cookie() function. Normally that function will store $this->userdata, but
// in this case that array contains custom data, which we do not want in the cookie.
$this->_set_cookie($cookie_userdata);
}
// --------------------------------------------------------------------
/**
* 创建一个新的session
*/
function sess_create()
{
//保证sessid 安全唯一
$sessid = '';
while (strlen($sessid) < 32)
{
$sessid .= mt_rand(0, mt_getrandmax());
}
$sessid .= $this->CI->input->ip_address();
$this->userdata = array(
'session_id'=> md5(uniqid($sessid, TRUE)),
'ip_address'=> $this->CI->input->ip_address(),
'user_agent'=> substr($this->CI->input->user_agent(), 0, 120),
'last_activity'=> $this->now,
'user_data'=> ''
);
// Save the data to the DB if needed
if ($this->sess_use_database === TRUE)
{
$this->CI->db->query($this->CI->db->insert_string($this->sess_table_name, $this->userdata));
}
// Write the cookie
$this->_set_cookie();
}
// --------------------------------------------------------------------
/**
* 更新session
*/
function sess_update()
{
// 默认五分钟更新
if (($this->userdata['last_activity'] + $this->sess_time_to_update) >= $this->now)
{
return;
}
// Save the old session id so we know which record to
// update in the database if we need it
$old_sessid = $this->userdata['session_id'];
$new_sessid = '';
while (strlen($new_sessid) < 32)
{
$new_sessid .= mt_rand(0, mt_getrandmax());
}
// To make the session ID even more secure we'll combine it with the user's IP
$new_sessid .= $this->CI->input->ip_address();
// Turn it into a hash
$new_sessid = md5(uniqid($new_sessid, TRUE));
// Update the session data in the session data array
$this->userdata['session_id'] = $new_sessid;
$this->userdata['last_activity'] = $this->now;
// _set_cookie() will handle this for us if we aren't using database sessions
// by pushing all userdata to the cookie.
$cookie_data = NULL;
// 更新数据库中几率
if ($this->sess_use_database === TRUE)
{
// set cookie explicitly to only have our session data
$cookie_data = array();
foreach (array('session_id','ip_address','user_agent','last_activity') as $val)
{
$cookie_data[$val] = $this->userdata[$val];
}
$this->CI->db->query($this->CI->db->update_string($this->sess_table_name, array('last_activity' => $this->now, 'session_id' => $new_sessid), array('session_id' => $old_sessid)));
}
// 重新写入session
$this->_set_cookie($cookie_data);
}
// --------------------------------------------------------------------
/**
*销毁当前所有session数据
*/
function sess_destroy()
{
// Kill the session DB row
if ($this->sess_use_database === TRUE && isset($this->userdata['session_id']))
{
$this->CI->db->where('session_id', $this->userdata['session_id']);
$this->CI->db->delete($this->sess_table_name);
}
// Kill the cookie
setcookie(
$this->sess_cookie_name,
addslashes(serialize(array())),
($this->now - 31500000),
$this->cookie_path,
$this->cookie_domain,
0
);
// Kill session data
$this->userdata = array();
}
// --------------------------------------------------------------------
/**
* 获取session数组指定元素的值
*/
function userdata($item)
{
return ( ! isset($this->userdata[$item])) ? FALSE : $this->userdata[$item];
}
// --------------------------------------------------------------------
/**
* 获取所有session数据
*/
function all_userdata()
{
return $this->userdata;
}
// --------------------------------------------------------------------
/**
* 添加和修改自定义的session数据
*/
function set_userdata($newdata = array(), $newval = '')
{
if (is_string($newdata))
{
$newdata = array($newdata => $newval);
}
//支持数组组合方式
if (count($newdata) > 0)
{
foreach ($newdata as $key => $val)
{
$this->userdata[$key] = $val;
}
}
$this->sess_write();
}
// --------------------------------------------------------------------
/**
* 删除session数组中的元素，
*/
function unset_userdata($newdata = array())
{
if (is_string($newdata))
{
$newdata = array($newdata => '');
}
if (count($newdata) > 0)
{
foreach ($newdata as $key => $val)
{
unset($this->userdata[$key]);
}
}
$this->sess_write();
}
// ------------------------------------------------------------------------
/**
* Add or change flashdata, only available
* until the next request
*
* @accesspublic
* @parammixed
* @paramstring
* @returnvoid
*/
function set_flashdata($newdata = array(), $newval = '')
{
if (is_string($newdata))
{
$newdata = array($newdata => $newval);
}
if (count($newdata) > 0)
{
foreach ($newdata as $key => $val)
{
$flashdata_key = $this->flashdata_key.':new:'.$key;
$this->set_userdata($flashdata_key, $val);
}
}
}
// ------------------------------------------------------------------------
/**
* CI支持闪出数据也就是说 Session数据只对下次服务器请求可用,有时候如果你还想在下个请求后的请求还有效。。。
* keep_flashdata功能就是讲持续保持闪出数据，使其在下个请求也有效
*/
function keep_flashdata($key)
{
//将闪出数据标记成new
$old_flashdata_key = $this->flashdata_key.':old:'.$key;
$value = $this->userdata($old_flashdata_key);
$new_flashdata_key = $this->flashdata_key.':new:'.$key;
$this->set_userdata($new_flashdata_key, $value);
}
// ------------------------------------------------------------------------
/**
* 获取闪出数据
*/
function flashdata($key)
{
$flashdata_key = $this->flashdata_key.':old:'.$key;
return $this->userdata($flashdata_key);
}
// ------------------------------------------------------------------------
/**
* 将闪出数据标记成old，以便_flashdata_sweep清除数据
*/
function _flashdata_mark()
{
$userdata = $this->all_userdata();
foreach ($userdata as $name => $value)
{
$parts = explode(':new:', $name);
if (is_array($parts) && count($parts) === 2)
{
$new_name = $this->flashdata_key.':old:'.$parts[1];
$this->set_userdata($new_name, $value);
$this->unset_userdata($name);
}
}
}
// ------------------------------------------------------------------------
/**
* 将标记成old的闪出数据闪出
*/
function _flashdata_sweep()
{
$userdata = $this->all_userdata();
foreach ($userdata as $key => $value)
{
if (strpos($key, ':old:'))
{
$this->unset_userdata($key);
}
}
}
//获取当前时间
function _get_time()
{
if (strtolower($this->time_reference) == 'gmt')
{
$now = time();
$time = mktime(gmdate("H", $now), gmdate("i", $now), gmdate("s", $now), gmdate("m", $now), gmdate("d", $now), gmdate("Y", $now));
}
else
{
$time = time();
}
return $time;
}
// --------------------------------------------------------------------
/**
* 写入session cookie
*
*/
function _set_cookie($cookie_data = NULL)
{
if (is_null($cookie_data))
{
$cookie_data = $this->userdata;
}
// 序列化数组
$cookie_data = $this->_serialize($cookie_data);
//加密数据
if ($this->sess_encrypt_cookie == TRUE)
{
$cookie_data = $this->CI->encrypt->encode($cookie_data);
}
else
{
// if encryption is not used, we provide an md5 hash to prevent userside tampering
$cookie_data = $cookie_data.md5($cookie_data.$this->encryption_key);
}
//sess_expire_on_close为TRUE则，浏览器关闭，session失效
$expire = ($this->sess_expire_on_close === TRUE) ? 0 : $this->sess_expiration + time();
// Set the cookie
setcookie(
$this->sess_cookie_name,
$cookie_data,
$expire,
$this->cookie_path,
$this->cookie_domain,
$this->cookie_secure
);
}
// --------------------------------------------------------------------
/**
* 序列化数组
*/
function _serialize($data)
{
if (is_array($data))
{
foreach ($data as $key => $val)
{
if (is_string($val))
{
$data[$key] = str_replace('\\', '{{slash}}', $val);
}
}
}
else
{
if (is_string($data))
{
$data = str_replace('\\', '{{slash}}', $data);
}
}
return serialize($data);
}
// --------------------------------------------------------------------
/**
* 反序列化数组
*/
function _unserialize($data)
{
$data = @unserialize(strip_slashes($data));
if (is_array($data))
{
foreach ($data as $key => $val)
{
if (is_string($val))
{
$data[$key] = str_replace('{{slash}}', '\\', $val);
}
}
return $data;
}
return (is_string($data)) ? str_replace('{{slash}}', '\\', $data) : $data;
}
// --------------------------------------------------------------------
/**
* 回收/删除数据库中失效的session信息
*/
function _sess_gc()
{
if ($this->sess_use_database != TRUE)
{
return;
}
srand(time());
if ((rand() % 100) < $this->gc_probability)
{
$expire = $this->now - $this->sess_expiration;
$this->CI->db->where("last_activity < {$expire}");
$this->CI->db->delete($this->sess_table_name);
log_message('debug', 'Session garbage collection performed.');
}
}
}