What are the security implications of using cookies, Local Storage, and WebWorker in PHP for tracking visited links?

When using cookies, Local Storage, and WebWorker in PHP for tracking visited links, there are security implications such as potential data leakage, cross-site scripting attacks, and unauthorized access to sensitive information. To address these concerns, it is important to properly sanitize and validate user input, use secure HTTPS connections, implement proper access controls, and regularly update and patch any security vulnerabilities.

// Example of implementing secure access controls for tracking visited links
if($_SERVER['REQUEST_METHOD'] == 'POST') {
    // Validate and sanitize input data
    $visitedLink = filter_input(INPUT_POST, 'visited_link', FILTER_SANITIZE_URL);

    // Implement secure access controls
    if(strpos($visitedLink, 'https://example.com') === 0) {
        // Track the visited link
        // Code to track the link goes here
    } else {
        // Log unauthorized access attempt
        // Code to log unauthorized access goes here
    }
}