Kafka\Protocol\Encoder::encodeMessageSet PHP Method

    public static function encodeMessageSet($messages, $compression = self::COMPRESSION_NONE)
    {
        if (!is_array($messages)) {
            $messages = array($messages);
        }
        $data = '';
        foreach ($messages as $message) {
            $tmpMessage = self::_encodeMessage($message, $compression);
            // int64 -- message offset     Message
            $data .= self::pack(self::BIT_B64, 0) . self::encodeString($tmpMessage, self::PACK_INT32);
        }
        return $data;
    }