很多時(shí)候我們需要對(duì)數(shù)據(jù)進(jìn)行加密解密，比如有些數(shù)據(jù)需要保存到cookie中，但又不能被用戶輕易得到這些數(shù)據(jù)，這時(shí)我們就需要加密這些數(shù)據(jù)保存到cookie中，等我們需要使用它們的時(shí)候再解密。

// 加密數(shù)據(jù)并寫到cookie里
$cookie_data = $this -> encrypt("nowamagic", $data);
                  
$cookie = array(
    'name'   => '$data',
    'value'  => $cookie_data,
    'expire' => $user_expire,
    'domain' => '',
    'path'   => '/',
    'prefix' => ''
);
$this->input->set_cookie($cookie);
  
// 加密
public function encrypt($key, $plain_text) {  
    $plain_text = trim($plain_text);  
    $iv = substr(md5($key), 0,mcrypt_get_iv_size (MCRYPT_CAST_256,MCRYPT_MODE_CFB));  
    $c_t = mcrypt_cfb (MCRYPT_CAST_256, $key, $plain_text, MCRYPT_ENCRYPT, $iv);  
    return trim(chop(base64_encode($c_t)));  
}  
 
使用的時(shí)候再解密：
if( isset($_COOKIE['data']) )
{
    //用cookie給session賦值
    $_SESSION['data'] = decrypt("nowamagic", $_COOKIE['data']);
}
  
function decrypt($key, $c_t) {  
    $c_t = trim(chop(base64_decode($c_t)));  
    $iv = substr(md5($key), 0,mcrypt_get_iv_size (MCRYPT_CAST_256,MCRYPT_MODE_CFB));  
    $p_t = mcrypt_cfb (MCRYPT_CAST_256, $key, $c_t, MCRYPT_DECRYPT, $iv);  
    return trim(chop($p_t));  
}