PHP 登录类（ PHP 重定向代码）

PHP 登录类（ PHP 重定向代码） class Auth{    var $user_id;    var $username;    var $password;    var $ok;    var $salt = "34asdf34";    var $domain = ".domain.com";     function Auth()    {        global $db;         $this->user_id = 0;        $this->username = "Guest";        $this->ok = false;         if(!$this->check_session()) $this->check_cookie();         return $this->ok;    }     function check_session()    {        if(!empty($_SESSION['auth_username']) && !empty($_SESSION['auth_password']))            return $this->check($_SESSION['auth_username'], $_SESSION['auth_password']);        else            return false;    }     function check_cookie()    {        if(!empty($_COOKIE['auth_username']) && !empty($_COOKIE['auth_password']))            return $this->check($_COOKIE['auth_username'], $_COOKIE['auth_password']);        else            return false;    }     function login($username, $password)    {        global $db;        $db->query("SELECT user_id FROM users WHERE username = '$username' AND password = '$password'");        if(mysql_num_rows($db->result) == 1)        {            $this->user_id = mysql_result($db->result, 0, 0);            $this->username = $username;            $this->ok = true;             $_SESSION['auth_username'] = $username;            $_SESSION['auth_password'] = md5($password . $this->salt);            setcookie("auth_username", $username, time()+60*60*24*30, "/", $this->domain);            setcookie("auth_password", md5($password . $this->salt), time()+60*60*24*30, "/", $this->domain);             return true;        }        return false;    }             function check($username, $password)    {        global $db;        $db->query("SELECT user_id, password FROM users WHERE username = '$username'");        if(mysql_num_rows($db->result) == 1)        {            $db_password = mysql_result($db->result, 0, 1);            if(md5($db_password . $this->salt) == $password)            {                $this->user_id = mysql_result($db->result, 0, 0);                $this->username = $username;                $this->ok = true;                return true;            }        }                    return false;    }     function logout()    {        $this->user_id = 0;        $this->username = "Guest";        $this->ok = false;         $_SESSION['auth_username'] = "";        $_SESSION['auth_password'] = "";         setcookie("auth_username", "", time() - 3600, "/", $this->domain);        setcookie("auth_password", "", time() - 3600, "/", $this->domain);    } }