What are the potential pitfalls of passing variables using cookies in PHP?

Passing variables using cookies in PHP can potentially expose sensitive information to security risks, such as data tampering or interception. To mitigate these risks, it is recommended to encrypt the data stored in cookies to prevent unauthorized access.

// Encrypt the variable before storing it in a cookie
$variable = "sensitive_data";
$encrypted_variable = openssl_encrypt($variable, 'AES-128-CBC', 'secret_key', 0, 'random_iv');
setcookie('encrypted_variable', $encrypted_variable, time() + 3600, '/');