在PHP中使用rdkafka處理再平衡，你需要監聽rd_kafka_event_rebalance事件。這個事件會在消費者組重新分配分區時觸發。以下是一個簡單的示例，展示了如何在PHP中使用rdkafka處理再平衡：

1. 首先，確保你已經安裝了php-rdkafka擴展。你可以使用PECL或者從源碼編譯安裝。安裝完成后，確保在你的php.ini文件中啟用了它。

2. 創建一個消費者實例，并加入消費者組：

<?php
require 'vendor/autoload.php'; // 引入composer自動生成的autoload文件

use RdKafka\Conf;
use RdKafka\Consumer;
use RdKafka\Event;

$conf = new Conf();
$conf->set('group.id', 'myGroup'); // 設置消費者組ID
$conf->set('bootstrap.servers', 'localhost:9092'); // 設置Kafka服務器地址
$conf->set('auto.offset.reset', 'earliest'); // 設置自動偏移量重置策略

$consumer = new Consumer($conf);
$consumer->subscribe(['myTopic']); // 訂閱主題

$running = true;
while ($running) {
    $event = $consumer->consume(120 * 1000); // 消費消息，超時時間為120秒

    switch ($event->err) {
        case RD_KAFKA_RESP_ERR__PARTITION_EOF:
            echo "Reached end of partition event\n";
            break;
        case RD_KAFKA_RESP_ERR__TIMED_OUT:
            echo "Timed out\n";
            break;
        case RD_KAFKA_RESP_ERR__PARTITION_NOT_FOUND:
            echo "Partition not found\n";
            break;
        case RD_KAFKA_RESP_ERR__UNKNOWN:
            echo "Unknown error\n";
            break;
        default:
            if ($event->err) {
                throw new \Exception($event->errstr(), $event->err);
            }

            switch ($event->type) {
                case Event::EVENT_REBALANCE:
                    echo "Rebalance event occurred\n";
                    // 處理再平衡事件
                    handleRebalanceEvent($consumer, $event);
                    break;
                case Event::EVENT_OFFSET_COMMIT:
                    echo "Offset commit event occurred\n";
                    break;
                case Event::EVENT_ERROR:
                    echo "Error event occurred\n";
                    break;
                case Event::EVENT_END_OF_PARTITION:
                    echo "End of partition event occurred\n";
                    break;
                case Event::EVENT_NEW_TOPIC:
                    echo "New topic event occurred\n";
                    break;
                case Event::EVENT_DEL_TOPIC:
                    echo "Deleted topic event occurred\n";
                    break;
                case Event::EVENT_CACHED:
                    echo "Cached event occurred\n";
                    break;
                default:
                    break;
            }
            break;
    }
}

$consumer->close();

3. 在handleRebalanceEvent函數中處理再平衡事件：

function handleRebalanceEvent(Consumer $consumer, Event $event) {
    switch ($event->err) {
        case RD_KAFKA_RESP_ERR__PARTITION_EOF:
            echo "Reached end of partition event\n";
            break;
        case RD_KAFKA_RESP_ERR__TIMED_OUT:
            echo "Timed out\n";
            break;
        case RD_KAFKA_RESP_ERR__PARTITION_NOT_FOUND:
            echo "Partition not found\n";
            break;
        case RD_KAFKA_RESP_ERR__UNKNOWN:
            echo "Unknown error\n";
            break;
        default:
            if ($event->err) {
                throw new \Exception($event->errstr(), $event->err);
            }
            break;
    }

    // 獲取再平衡事件的相關信息
    $topic = $event->topic;
    $partition = $event->partition;
    $new_partition_cnt = $event->new_partition_cnt;
    $member_id = $event->member_id;
    $client_id = $event->client_id;

    echo "Rebalance event for topic: $topic, partition: $partition, new_partition_cnt: $new_partition_cnt, member_id: $member_id, client_id: $client_id\n";

    // 在這里處理再平衡事件，例如更新本地存儲的分區信息，重新分配消費者等
}

這個示例展示了如何在PHP中使用rdkafka處理再平衡事件。當消費者組重新分配分區時，handleRebalanceEvent函數會被調用，你可以在這個函數中實現你的再平衡處理邏輯。