private static function getRelativePath($from, $to)
    {
        $from = explode('/', $from);
        $to = explode('/', $to);
        $relPath = $to;

        foreach ($from as $depth => $dir) {
            // find first non-matching dir
            if (isset($to[$depth]) && $dir === $to[$depth]) {
                // ignore this directory
                array_shift($relPath);
            } else {
                // get number of remaining dirs to $from
                $remaining = count($from) - $depth;
                if ($remaining > 1) {
                    // add traversals up to first matching dir
                    $padLength = (count($relPath) + $remaining - 1) * -1;
                    $relPath = array_pad($relPath, $padLength, '..');
                    break;
                } else {
                    $relPath[0] = './'.$relPath[0];
                }
            }
        }

        return implode('/', $relPath);
    }