Twig filter that returns a default value if the given one is null

IfNullExtension.php

<?php

/*
 * Installation:
 * =============
 * # services.yml
 * services:
 *     # ...
 *     acme.twig.if_null_extension:
 *         class: Acme\AcmeBundle\Twig\IfNullExtension
 *         tags:
 *             - { name: twig.extension }
 * 
 * Usage:
 * ======
 * {{ entity.lastName | ifNull("-") }}
 */

namespace Acme\AcmeBundle\Twig;

class IfNullExtension extends \Twig_Extension
{
    public function getFilters()
    {
        return array(
            new \Twig_SimpleFilter("ifNull", array($this, "ifNullFilter"))
        );
    }

    public function ifNullFilter($value, $default)
    {
        if (null === $value) {
            return $default;
        } else {
            return $value;
        }
    }

    public function getName()
    {
        return "ifNull_extension";
    }
}