Are there any specific PHP functions or libraries recommended for handling user authentication and displaying logged-in users?

When handling user authentication in PHP, it is recommended to use the password_hash() function for securely hashing passwords and password_verify() function for verifying passwords. For displaying logged-in users, you can use sessions to store user information once they have successfully logged in.

// User authentication
$password = 'password123';
$hashed_password = password_hash($password, PASSWORD_DEFAULT);

if (password_verify($password, $hashed_password)) {
    echo 'Password is correct';
} else {
    echo 'Password is incorrect';
}

// Displaying logged-in users
session_start();

$_SESSION['user_id'] = 123;
$_SESSION['username'] = 'john_doe';

echo 'Logged in as ' . $_SESSION['username'];