Batch save data to mailchimp

//Batch list user payment to Mailchimp
    $request_body_parameters = new stdClass();
    $request_body_parameters->operations = array();
    foreach ($sendEmail as $this_email) {
        json_encode($this_email);
        $email = $this_email['email'];
        $first = $this_email['firstName'];
        $last = $this_email['lastName'];

        $o = new stdClass();
        $o->method = 'PUT';
        $o->path = 'lists/' . MAILCHIMP_LIST_FESTIVAL_HK . '/members/' . md5(strtolower($email));
        $o->body = json_encode(array(
            'email_address' => $email,
            'status' => 'subscribed',
            "merge_fields" => [
                'FNAME' => $first,
                'LNAME' => $last
            ]
        ));
        $request_body_parameters->operations[] = $o;
    }
    $response = wp_remote_post('https://' . substr(MAILCHIMP_APIKEY, strpos(MAILCHIMP_APIKEY, '-') + 1) . '.api.mailchimp.com/3.0/batches', array(
        'method' => 'POST',
        'headers' => array(
            'Authorization' => 'Basic ' . base64_encode('user:' . MAILCHIMP_APIKEY)
        ),
        'body' => json_encode($request_body_parameters)
    ));
    if (wp_remote_retrieve_response_message($response) == 'OK') {
        $response_body_parameters = json_decode(wp_remote_retrieve_body($response));
    }

//you can remove foreach