What potential security risks are associated with using cookies for login functionality in PHP?

Using cookies for login functionality in PHP can pose potential security risks such as cookie tampering, session hijacking, and cross-site scripting attacks. To mitigate these risks, it is recommended to use secure and HttpOnly flags when setting cookies, implement proper session management techniques, and validate and sanitize user input to prevent injection attacks.

// Set secure and HttpOnly flags for cookies
setcookie('user', $username, time() + 3600, '/', '', true, true);