PHP authentication with multiple domains and subdomains

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.

To keep your sessions going across multiple domains, you need to use session_set_cookie_params(). With that, you can specify your domain. For example...

session_set_cookie_params(10000, "/", ".main.com");

That will set the session timeout at 10,000 seconds for all documents under the site root, and for all subdomains of main.com.

You should call session_set_cookie_params() before you do session_start().