What are some potential pitfalls of trying to store user data on the client's computer using PHP?

One potential pitfall of storing user data on the client's computer using PHP is the lack of security. Client-side storage methods like cookies or local storage are susceptible to attacks such as cross-site scripting (XSS) or data tampering. To mitigate this risk, sensitive user data should be stored on the server-side and accessed securely through authenticated requests.

// Store sensitive user data on the server-side
$userData = [
    'username' => 'example_user',
    'email' => 'user@example.com',
    'password' => 'hashed_password'
];

// Access user data securely through authenticated requests
if ($authenticated) {
    // Retrieve user data from server-side storage
    $username = $userData['username'];
    $email = $userData['email'];
}