How to make library in cakephp

1. Make a class in lib folder and Save it url_encoder.php

<?php

class UrlEncoder {

       public static function encode($url) {

                  return preg_replace(array('/\+/', '/\//'), array('-', '_'), base64_encode($url));

        }

 public static function decode($url_encoded) {

                 return base64_decode(preg_replace(array('/-/', '/_/'), array('+', '/'), $url_encoded));

        }

}
?>

2. Now implement in your controller , if you want to initialize lib initially then define it in before filter function

function beforeFilter()

{
       parent::beforeFilter();
      App::import('Lib', 'UrlEncoder');
}

3. Now how to use its function

UrlEncoder::encode($contact_id);

UrlEncoder::decode($contact_id) ;