Description

chapter: http://www.symfony-project.com/book/trunk/07-Inside-the-View-Layer#Adding%20Your%20Own%20Helpers

there should be a hint, that it is possible to extend a symfony helper by defining a file called as the helpter to extend and start the file with the following statement:

require_once('symfony/helper/NumberHelper.php');

see for example: http://www.symfony-project.com/snippets/snippet/167