PHP 登录类

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);
 }
 
}