How to implement cross-domain automatic login in php

With the increasing popularity of web applications, cross-domain problems have become increasingly difficult to avoid. When users access one domain name from another domain name, they may need to automatically log in between different domain names to improve user experience. In this case, PHP is an effective choice for automatic cross-domain login. In this article, we will introduce how to use PHP to implement cross-domain automatic login.

1. Obtain cross-domain cookies

To achieve cross-domain automatic login, you first need to obtain the user's cookie under the source domain name. Since cookies are not accessible across domains, we need to use ajax to submit a request to the server to obtain cookies under the source domain name.

On the source domain name server, we need to create a PHP file named "get_cookie.php" to obtain cookies. The code is as follows:

<?php header(&#39;Access-Control-Allow-Origin: *&#39;);
if ($_SERVER[&#39;REQUEST_METHOD&#39;] == &#39;POST&#39;) {
  if (isset($_COOKIE[&#39;user&#39;])) {
    echo $_COOKIE[&#39;user&#39;];
  } else {
    echo &#39;Cookie not found.&#39;;
  }
}
?>

In the code, we use the header function to set the "Access-Control-Allow-Origin" header file to allow cross-domain access. If the user cookie exists, the cookie is returned to the caller, otherwise "Cookie not found." is returned.

2. Send Cookies across domains

After obtaining the source domain Cookie, we need to send it to the target domain. To ensure security, we cannot send cookie values ​​directly to the target domain. Instead, we need to use encryption technology to process cookies. In this example, we choose to use Base64 encoding technology.

On the target domain name server, we need to create a PHP file named "login.php" to process cookies sent from the source domain. The code is as follows:

<?php $user = $_POST[&#39;user&#39;];
if (!empty($user)) {
  $user = base64_decode($user);
  $user_arr = explode(&#39;,&#39;, $user);
  if (count($user_arr) == 2) {
    $username = $user_arr[0];
    $password = $user_arr[1];
    //check user credentials and login
    //...
    echo &#39;success&#39;;
  } else {
    echo &#39;Invalid cookie data.&#39;;
  }
} else {
  echo &#39;Cookie not found.&#39;;
}
?>

In the code, we first use the $_POST variable to obtain the cookie sent from the source domain. We then Base64 decode the cookie and split it into username and password. Next, we can log in using the username and password and return the "success" string to the caller after successful login. If the cookie data is invalid, "Invalid cookie data." is returned.

3. Use iframe to realize automatic jump

Finally, we need to use iframe to automatically jump between the source domain and the target domain. On the source domain, we create an HTML file named "login.html" with the following code:

nbsp;html>


<meta>
<title>Cross-Domain Login</title>
<script></script>
<script>
$(function() {
  $.ajax({
    url: &#39;https://example.com/get_cookie.php&#39;,
    method: &#39;POST&#39;,
    success: function(data) {
      var iframe = $(&#39;<iframe/>&#39;, {
        src: &#39;https://targetdomain.com/login.php&#39;,
        style: &#39;display:none;&#39;
      });
      $(&#39;body&#39;).append(iframe);
      iframe.load(function() {
        iframe.contents().find(&#39;body&#39;).append(&#39;<form method="post" action="https://targetdomain.com/login.php"><input type="hidden" name="user" value="&#39; + data + &#39;">&#39;);
        iframe.contents().find(&#39;form&#39;).submit();
      });
    },
    error: function() {
      alert(&#39;Failed to get cookie.&#39;);
    }
  });
});
</script>


<p>Loading...</p>

In the code, we use the jQuery library to initiate an ajax request to obtain the source domain cookie. Then, we created a hidden iframe and added it to the body element. When the iframe finishes loading, we add the cookie to a POST form and use the form to initiate a login request on the target domain.

When the user opens "https://sourcedomain.com/login.html", the page will automatically send a POST request to obtain the cookie. Then, the page will open a hidden iframe page and automatically fill in the login information to complete the automatic login.

Summary

This article introduces the method of using PHP to implement cross-domain automatic login. First we use an ajax request to get the cookie on the source domain, then we encrypt the cookie using Base64 encoding and decrypt it using a POST form on the target domain. Finally, we use iframes to automatically jump between the source and target domains. Using this method can provide users with a better experience while maintaining relatively high security, and it is worth mastering.

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