Wordpress helper: Get file URL

get_file_url.php

<?php

/**
 * get_file_url
 * 
 * Usage example:
 * 
 *  URL relative to the base file:
 *  get_file_url('styles.css', __FILE__);
 * 
 *  Or
 * 
 *  URL relative to the theme:
 *  get_file_url('css/styles.css');
 * 
 * @author JoseRobinson.com
 * @link https://gist.github.com/jrobinsonc/8dcfb3280d93345d7ff4
 */
function get_file_url($file_name, $base_file = '')
{
    // URL relative to the theme.
    if ($base_file === '')
        return get_template_directory_uri() . "/{$file_name}";

    // URL relative to the base file.
    else
        return str_replace(get_template_directory(), get_template_directory_uri(), dirname($base_file) . '/' . $file_name);
}