Pony.fm/app/Library/CacheBusterAsset.php

<?php
use Assetic\Asset\BaseAsset;
use Assetic\Filter\FilterInterface;

/**
 * Class CacheBusterAsset
 * OH GOD IT BUUUUUUURNS
 *
 * Well, I may as well tell you why this awful class exists. So... Assetic doesn't quite support less's import
 * directive. I mean; it supports it insofar as Less itself supports it - but it doesn't take into account the
 * last modified time for imported assets. Since we only have one less file that imports everything else... well
 * you can see where this is going. This asset will let us override the last modified time for an entire collection
 * which allows me to write a custom mechanism for cache busting.
 */
class CacheBusterAsset extends BaseAsset
{
    private $_lastModified;

    /**
     * @param int $lastModified
     */
    public function __construct($lastModified)
    {
        $this->_lastModified = $lastModified;
        parent::__construct([], '', '', []);
    }

    public function load(FilterInterface $additionalFilter = null)
    {
    }

    public function getLastModified()
    {
        return $this->_lastModified;
    }
}