public static function start(PDO $pdo)
{
self::$pdo = $pdo;
self::$ctime = time();
self::$maxlifetime = ini_get("session.gc_maxlifetime");
self::$uip = !empty($_SERVER['HTTP_CLIENT_IP']) ? $_SERVER['HTTP_CLIENT_IP'] : (!empty($_SERVER['HTTP_X_FORWARDED_FOR']) ? $_SERVER['HTTP_X_FORWARDED_FOR'] : (!empty($_SERVER['REMOTE_ADDR']) ? $_SERVER['REMOTE_ADDR'] : ""));
//filter_var(self::$uip, FILTER_VALIDATE_IP) && self::$uip = '';
self::$uagent = !empty($_SERVER['HTTP_USER_AGENT']) ? $_SERVER['HTTP_USER_AGENT'] : "";
//注册过程， 让PHP自己处理session时，找这个函数指定的几个周期来完成
session_set_save_handler(array(__CLASS__, "open"), array(__CLASS__, "close"), array(__CLASS__, "read"), array(__CLASS__, "write"), array(__CLASS__, "destroy"), array(__CLASS__, "gc"));
session_start();
//开启会话
}