What are the advantages and disadvantages of using cookies versus sessions for managing user authentication in PHP?

When managing user authentication in PHP, both cookies and sessions can be used to store user information. Cookies are stored on the user's browser, while sessions are stored on the server. Advantages of using cookies: 1. Cookies can persist even after the user closes their browser, allowing for persistent authentication. 2. Cookies can be easily manipulated and read by JavaScript, providing more flexibility in client-side interactions. Disadvantages of using cookies: 1. Cookies can be vulnerable to attacks like cross-site scripting (XSS) and cross-site request forgery (CSRF). 2. Cookies have a limited storage capacity, which can be a limitation for storing large amounts of user data. Advantages of using sessions: 1. Sessions are stored on the server, making them more secure than cookies. 2. Sessions automatically expire after a specified period of inactivity, enhancing security. Disadvantages of using sessions: 1. Sessions require server-side resources to store and manage session data. 2. Sessions are not as easily accessible by client-side scripts compared to cookies. Overall, the choice between using cookies and sessions for managing user authentication in PHP depends on the specific requirements of the application in terms of security, persistence, and ease of access.

// Using sessions for user authentication
session_start();

// Set session variables
$_SESSION['user_id'] = $user_id;
$_SESSION['username'] = $username;

// Check if user is authenticated
if(isset($_SESSION['user_id'])) {
    // User is authenticated
    echo "User is authenticated";
} else {
    // User is not authenticated
    echo "User is not authenticated";
}