/**
 * session 数据库存储类
 *
 * @param 
 * @author 编程之家 jb51.cc jb51.cc
 **/
class Session {
 
 private static $session_id   = 0;
 private static $session_data  = array();
 private static $is_update   = FALSE;
 private static $is_del    = FALSE;
 private static $is_gc    = FALSE;
 private static $dbo    = NULL;  //数据库连接句柄
 private static $gc_max_time  = 1440;
 private static $table   = 'sessions';
 private static $pre_key   = 'weige';//session 密钥
 //捆绑使用哈
 private static $gc_rate_de  = 100;//代表分母
 private static $gc_rate_co  = 20;//代表分子
 
 private static $path   = '/';//保存路径
 private static $domain   = null; //域
 private static $secure   = false;//默认
 private static $httponly  = false;//默认
 /**
  * 获取数据库句柄  私有
  */
 private static function open() 
 {
  if (!self::$dbo) 
  {
   self::$dbo = Db::factory();
  }
  return TRUE;
 }
 /**
  * 设置
  * */
 public static function set($key,$val=NULL) 
 {
  
  self::open();
  $data = self::read();
  if ($data === FALSE)
  {
   $data = array();
  }
  if (!$val && is_array($key))
  {
   $data = $key;
  } 
  else if ($val && is_string($key))
  {
   $data[$key] = $val;
  }
  self::write($data);
  self::close();
 }
 /**
  *获取值 
  * 
  */
 public static function get($key=NULL) {
  self::open();
  self::$session_data = self::read();
  $ret = '';
  if (!$key) {
   $ret = self::$session_data;
  } else if(is_array(self::$session_data) && isset(self::$session_data[$key])) {
   $ret = self::$session_data[$key];
  }
  self::update(); 
  self::close();
  return $ret;
 }
 /**
  * 删除或者重置
  * */
 public static function del($key)
 {
  if (!self::$is_del) 
  {
   self::open();
   
   $val = self::read();
   
   if (isset($val[$key])) 
   {
    unset($val[$key]);
   }
   
   $session_id  = self::$session_id;
   $session_data  = serialize($val);
   $session_expire = TIME + self::get_gc_maxtime();
   self::$dbo->query("update ".self::$table." set value='$session_data',expiry='$session_expire' where session_id='$session_id'");
   self::close();
  }
  self::$is_del = TRUE;
 }
 /**
  * 销毁
  * 
  * */
 public static function destroy() 
 {
  $session_id   = self::get_session_id();
  $_COOKIE['WBSID'] = '';
  
  self::open();
  self::$dbo->query("delete from ".self::$table." where session_id='$session_id'");
  self::close();
 }
 
 
 /**
  * 读取  私有
  * */
 private static function read()
 {
  $session_id = self::$session_id;
  if (!$session_id) {
   $session_id = self::get_session_id();
  }
  
  if (!$session_id) return array();
  
  $user_agent = isset($_SERVER['HTTP_USER_AGENT']) ? md5($_SERVER['HTTP_USER_AGENT']) : '';
  $client_ip = Fun::getIp();
  $session_expire = TIME - self::get_gc_maxtime();
  
  $rs = self::$dbo->fetchRow("select session_id,value,agent,ip from ".self::$table."
   where session_id='$session_id' and expiry>'$session_expire'");
  
  if (!$rs || $rs['agent'] != $user_agent || $rs['ip'] != $client_ip) 
  {
   return FALSE;
  }
  
  self::$session_id = $rs['session_id'];
  return unserialize($rs['value']);
 }
 /**
  * session 写入   私有
  * */
 private static function write(array $session_data) 
 {
  $session_id = self::$session_id;
  
  if (!$session_id)
  {
   $session_id = self::get_session_id();
  }
  
  $session_expire = TIME + self::get_gc_maxtime();
  
  $user_agent = isset($_SERVER['HTTP_USER_AGENT']) ? md5($_SERVER['HTTP_USER_AGENT']) : '';
  $client_ip  = Fun::getIp();
  
  $session_data = serialize($session_data);
  
  if (self::$session_id && self::$session_id === $session_id) 
  {
   self::$dbo->query("update ".self::$table." set value='$session_data',expiry='$session_expire',agent='$user_agent',ip='$client_ip' where session_id='$session_id'");
  } 
  else 
  {
   self::$session_id = $session_id = self::create_session_id();
   self::$dbo->query("insert into ".self::$table."(session_id,expiry,ip) 
    values('$session_id','$session_data','$session_expire','$user_agent','$client_ip')");
  }
  return true;
 }
 /**
  * session 更新   私有
  * */
 private static function update() 
 {
  if (!self::$is_update) 
  {
   $session_id = self::$session_id;
   $session_expire = TIME + self::get_gc_maxtime();
   self::$dbo->query("update ".self::$table." set expiry='$session_expire' where session_id='$session_id'");
  }
  self::$is_update = TRUE;
 }
 
 private static function close() 
 {
  if (!self::$is_gc && mt_rand(1,self::$gc_rate_de)%self::$gc_rate_co == 0) 
  {
   self::gc();
  }
  self::$is_gc = TRUE;
 }
 /**
  * 过期session 清除  随机触发
  * */
 private static function gc() 
 {
  
  $session_expire = TIME - self::get_gc_maxtime();
   self::$dbo->query("delete from ".self::$table." where expiry<'$session_expire'");
 }
 
 private static function get_session_id() 
 {
  if (isset($_COOKIE['WBSID']) && strlen($_COOKIE['WBSID'])==32) 
  {
   $sid = $_COOKIE['WBSID'];
   setcookie('WBSID',$sid,TIME + self::get_gc_maxtime(),self::$path,self::$domain,self::$secure,self::$httponly);
   return $sid;
  }
  return null;
 }
 
 private static function create_session_id() 
 {
  $sid = self::get_session_id();
  if (!$sid) 
  {
   $sid = Fun::getIp() . TIME . microtime(TRUE) . mt_rand(mt_rand(0,100),mt_rand(100000,90000000));
   $sid = md5(self::$pre_key . $sid);
   setcookie('WBSID',substr($sid,32),self::$httponly);
  }
  return $sid;
 }
 
 public static function get_gc_maxtime()
 {
  return  self::$gc_max_time;
 }
}


/***   代码来自编程之家 jb51.cc（jb51.cc）   ***/