What are the potential limitations and security concerns of trying to read cookies set by another server in PHP?

Reading cookies set by another server in PHP can pose potential security risks as it may lead to unauthorized access to sensitive information. To mitigate this risk, it is recommended to only read cookies set by your own server or trusted sources. If there is a legitimate need to access cookies from another server, consider implementing secure communication protocols such as HTTPS and validating the origin of the cookie.

// Check the domain of the cookie before reading it
if (strpos($_SERVER['HTTP_COOKIE'], 'cookie_name=') !== false && $_SERVER['HTTP_HOST'] === 'trusteddomain.com') {
    $cookie_value = $_COOKIE['cookie_name'];
    // Process the cookie value
} else {
    // Handle unauthorized access
}