What are the potential limitations or drawbacks of using cookies for user identification in PHP?

One potential limitation of using cookies for user identification in PHP is that they can be easily manipulated or tampered with by users, leading to security risks. To mitigate this risk, it's important to encrypt the cookie data before setting it and validate the data when retrieving it to ensure its integrity. 

// Encrypting cookie data before setting it
$userId = 123; // User ID to be stored in the cookie
$encryptedData = base64_encode(openssl_encrypt($userId, 'AES-256-CBC', 'secret_key', 0, '16charsofIV'));

// Setting the encrypted data in a cookie
setcookie('user_id', $encryptedData, time() + 3600, '/');

// Validating and decrypting the cookie data when retrieving it
if(isset($_COOKIE['user_id'])){
    $decryptedData = openssl_decrypt(base64_decode($_COOKIE['user_id']), 'AES-256-CBC', 'secret_key', 0, '16charsofIV');
    $userId = (int) $decryptedData;
}

Keywords

cookies user identification limitations drawbacks PHP

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