What are the potential pitfalls of trying to link user logins between different PHP scripts or applications?

When trying to link user logins between different PHP scripts or applications, potential pitfalls include security vulnerabilities, data inconsistency, and compatibility issues between different authentication systems. To solve this, it is recommended to use a centralized authentication system like OAuth or OpenID, which allows users to log in once and access multiple applications securely. 

// Example of implementing OAuth for centralized authentication

// Include OAuth library
require_once 'OAuth.php';

// Initialize OAuth client
$oauth = new OAuth('consumer_key', 'consumer_secret');

// Get request token
$request_token = $oauth->getRequestToken('https://example.com/oauth/request_token');

// Redirect user to authorization URL
header('Location: ' . $oauth->getAuthorizeURL($request_token));

// Once user authorizes, exchange request token for access token
$access_token = $oauth->getAccessToken('https://example.com/oauth/access_token');

Keywords

Session management cross-site scripting authentication CSRF protection database integration

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