Produce array

[tbachali...@gmail.com]

Hi all !
I want to send an array just with four fields, i am trying this way

 $topic->produce(RD_KAFKA_PARTITION_UA, 0, $result[$i]);

But consumer cant see it and i have the warning:
PHP Warning:  RdKafka\ProducerTopic::produce() expects parameter 3 to be string, array given in /var/www/html/new-tests/producer-new-test.php on line 28

Is there any other way to do this? 
Or what am i doing wrong?
Thank you in advance