Append a hash to the asset file for cache-busting

hash_assets_file.php

<?php
/**
 * Elixir asset helper
 *
 * @param string $file File name
 * @return string
 *
 * @throws \InvalidArgumentException
 */
function elixir($file)
{
    static $manifest = NULL;

    if (is_null($manifest))
    {
        $manifest = json_decode(file_get_contents(FCPATH . '/build/rev-manifest.json'), TRUE);
    }

    if (isset($manifest[$file]))
    {
        return '/build/' . $manifest[$file];
    }

    throw new InvalidArgumentException("File {$file} not defined in asset manifest.");
}