drupal 7 parameter encoding / decoding

encode-params.php

<?php
class MyUtils {
 
  public static function getHash($string) {
    return hash_hmac('sha256', $string, drupal_get_private_key(), false);
  }

  /**
   * Helper function to encode and hash data.
   */
  public static function encode($data) {
    $serialized = json_encode($data);
    $hmac       = static::getHash($serialized);
    $base64     = base64_encode($hmac . ':' . $serialized);
    return strtr($base64, '+/=', '-_.');
  }


  /**
   * Helper function to decode and verify data.
   *
   * @param string $string
   *   A Base64 encoded string created from
   * @return mixed|null
   */
  public static function decode($string) {
    $string = strtr($string, '-_.', '+/=');
    $decoded = base64_decode($string);
    list($hmac, $serialized) = explode(':', $decoded, 2) + array(null, null);
    if($hmac !== static::getHash($serialized)) {
      return null;
    }
    $data = @json_decode($serialized, true);
    return $data;
  }
 
}