php基于session实现数据库交互的类实例

<"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']) "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']) "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::$table."(session_id, value, expiry, agent, ip) 
    values('$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, 0, 32), TIME + self::get_gc_maxtime(), self::$path, self::$domain, self::$secure, self::$httponly);
  }
  return $sid;
 }
 public static function get_gc_maxtime()
 {
  return self::$gc_max_time;
 }
}