Cloudinary\Uploader::build_custom_headers PHP Method

    protected static function build_custom_headers($headers)
    {
        if ($headers == NULL) {
            return NULL;
        } elseif (is_string($headers)) {
            return $headers;
        } elseif ($headers == array_values($headers)) {
            return implode("\n", $headers);
        } else {
            $join_pair = function ($key, $value) {
                return $key . ": " . $value;
            };
            return implode("\n", array_map($join_pair, array_keys($headers), array_values($headers)));
        }
    }