据我所知，子域之间的跨会话很好，但它不会延续到一个全新的域.为此，您需要某种集中式数据方法或 API.

数据库方法:您必须创建一个远程 MySQL 数据访问，以便 domain2.com 可以访问 domain1.com 上的数据库.执行登录时，不仅应创建新会话，而且应将唯一的登录令牌(具有到期时间)放入 mysql 数据库.现在，对于从 domain1.com 到 domain2.com 的每个链接，您应该添加一个 $_GET 变量，该变量包含一个随机生成的会话 ID(md5 哈希就可以).domain2.com 收到访问者后，将获取 $_GET 变量，通过 MySQL 数据库运行它以查找登录令牌，如果匹配，则认为该用户已登录(并且可能嵌入 $_COOKIE 作为以及存储登录数据).这将使登录可以在两个完全不同的域之间转移.

API 方法:您需要创建一个 API 方法，以便 domain1.com 可以响应来自授权域的外部请求，以在用户被转发时检索登录令牌.此方法还要求所有从 domain1.com 到 domain2.com 的链接附加 $_GET 变量以传递唯一的会话哈希.然后在收到访问者后，domain2.com 将对 domain1.com/userapi.php(或任何您调用的文件)发出 curl() 请求，并且应该针对数据库中的内容测试变量.

这是我能解释的***的了..用代码写出来是一项重要的工作，所以我不能提交.但是从你的代码来看，你对 PHP 有很好的理解，所以我相信你会成功的！

祝你好运.

I have one main domain: main.com, subdomains: test1.main.com, test2.main.com and other domains one.com, two.com.

Now it's done like these:

ini_set("session.cookie_domain", ".main.com");

$domain = 'main.com';

login.php

$user = $db->query("SELECT id, login FROM users WHERE email=? AND password=?", 
array($email, $password), "rowassoc");

if($user)
{
  $_SESSION['user_id'] = $user['id'];
  $_SESSION['user_name'] = $user['login'];

  $time = 100000; 

  setcookie('email', $email, time() + $time, "/", "." . $domain);
  setcookie('password', $password, time() + $time, "/", "." . $domain);

  header('Location: http://' . $user['login'] . "." . $domain);
  exit;
}

added on each page:

if(!isset($_SESSION['user_id']))
{
  if(isset($_COOKIE['email']) && isset($_COOKIE['password']))
  {
    $email = $_COOKIE['email'];
    $password = $_COOKIE['password'];

    $user = $db->query("SELECT id, login FROM users WHERE email=? AND password=?",
    array($email, $password), "rowassoc");

    if($user)
    {
      $_SESSION['user_id'] = $user['id'];
      $_SESSION['user_name'] = $user['login'];
    }
  }
}
else
{
  $user = $db->query("SELECT id, login FROM users WHERE id=?", 
  array($_SESSION['user_id']), "rowassoc");


  if(!$user)
  {
    setcookie('email', '', time() , "/", "." . $domain);
    setcookie('password', '', time() , "/", "." . $domain);
    unset($_SESSION['user_id']);

    session_destroy();
    setcookie("PHPSESSID","",time(), "/", "." . $domain);
  }
  else
  {
    $_SESSION['user_id'] = $user['id'];
    $_SESSION['user_name'] = $user['login'];
  }
}

logout.php

if(isset($_SESSION['user_id']))
{
  setcookie('email', '', time() , "/", "." . $domain);
  setcookie('password', '', time() , "/", "." . $domain);
  unset($_SESSION['user_id']);
  unset($_SESSION['user_name']);

  session_destroy();
  setcookie("PHPSESSID","",time(), "/", "." . $domain);

  header('Location: /main');
  exit;
}

But it works only on domain main.com and its subdomains test1.main.com, test2.main.com.

I need to somehow save the session and on other domains one.com, two.com.

How best to do safe authentication, if there are solutions, i really confused, please tell with example.

As far as I know, crossing sessions between sub-domains is fine, but it won't carry over to a whole new domain. To do that you need some sort of centralized data method, or an API.

Database method: you will have to create a remote MySQL data access so that domain2.com can access the database on domain1.com. When a log-in is performed, not only should it create a new session, but a unique log-in token (with an expiry time) should be put into the mysql database. Now, for every link that goes from domain1.com to domain2.com, you should add a $_GET variable that contains a randomly generated session id (md5 hash will do). domain2.com, upon receiving the visitor, will take the $_GET variable, run it through the MySQL database to find the login token, and if there is a match, consider that user to be logged on (and perhaps embed a $_COOKIE as well to store the login data). This will make the log-in transferrable between two completely different domains.

API method: you need to create an API method, so that domain1.com can respond to an external request from authorized domains to retrieve the login token upon a user being forwarded. This method will also require that all links going from domain1.com to domain2.com to be appended with a $_GET variable to pass the unique session hash. Then upon receiving the visitor, domain2.com will do a curl() request to domain1.com/userapi.php (or whatever you call the file) and the variables should be tested against what's in the database.

This is the best I can explain it.. to write this out in code is a significant piece of work so I cannot commit. But judging by your code, you have a very good understanding of PHP so I'm confident you will pull this off!

Good luck mate.