Symfony2 Twig extension for generating gravatar links for stuff. Accepts objects with a `getEmail()` function, arrays with an `email` key, or just a string.

GravatarExtension.php

<?php
/**
 * This goes in your services.yml:
 * 
 * services:
 *     example.twig.gravatar_extension:
 *         class: My\ExampleBundle\Twig\GravatarExtension
 *         tags:
 *             - { name: twig.extension }
 */
namespace My\ExampleBundle\Twig;

class GravatarExtension extends \Twig_Extension
{
    private $gravatar_base = '//gravatar.com/avatar/';

    public function getFilters()
    {
        return array(
            new \Twig_SimpleFilter('gravatar', array($this, 'gravatarFilter')),
        );
    }

    public function gravatarFilter($input, $size = 40, $default = 'identicon')
    {
        if (is_object($input)) {
            $input = $input->getEmail();
        }
        if (is_array($input)) {
            $input = $input['email'];
        }

        $final = $this->gravatar_base . md5( strtolower( $input ) ) . '.png?s=' . $size . '&d=' . $default;

        return $final;
    }

    public function getName()
    {
        return 'gravatar_extension';
    }
}