How to Share PHP Sessions Across Subdomains?

Cross-Subdomain Session Sharing in PHP

When managing user sessions across multiple subdomains, ensuring seamless login and data persistence is crucial. In this scenario, you need to allow subdomains to access the authorized sessions created on the primary domain.

You have tried setting the session.cookie_domain in your php.ini to .example.com to enable cross-subdomain cookie sharing. However, your code doesn't appear to be reading the shared session data.

To resolve this, try the following:

// sub1.example.com  
session_name('YOUR_SESSION_NAME'); // Add a unique name, e.g., 'my_session'
session_set_cookie_params(0, '/', '.example.com');
session_start();
print session_id() . "<br>";
$_SESSION['Registered'] = 1;
echo '<a href="http://auth.example.com/test.php">Change Sites</a>';

// auth.example.com
session_name('YOUR_SESSION_NAME'); // Match the name from sub1.example.com
session_set_cookie_params(0, '/', '.example.com');
session_start();
print session_id() . "<br>";
$_SESSION['Checked'] = 1;
print_r($_SESSION);

By adding session_name('YOUR_SESSION_NAME'); before setting the cookie parameters, you ensure that the subdomains use the same session name. This allows them to access and modify the shared session data. Replace YOUR_SESSION_NAME with a unique identifier.

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