如何使用php Elasticsearch实现全文搜索的高亮显示？

require 'vendor/autoload.php';

use ElasticsearchClientBuilder;

$client = ClientBuilder::create()->build();

$params = [
    'index' => 'my_index',
    'body' => [
        [
            'title' => 'Title 1',
            'content' => 'This is the content of document 1.'
        ],
        [
            'title' => 'Title 2',
            'content' => 'This is the content of document 2.'
        ],
        [
            'title' => 'Title 3',
            'content' => 'This is the content of document 3.'
        ]
    ]
];

$client->index($params);

$searchParams = [
    'index' => 'my_index',
    'type' => 'my_type',
    'body' => [
        'query' => [
            'match' => [
                'content' => 'search keyword'
            ]
        ],
        'highlight' => [
            'fields' => [
                'content' => new stdClass()
            ]
        ]
    ]
];

$response = $client->search($searchParams);

foreach ($response['hits']['hits'] as $hit) {
    $highlight = $hit['highlight'];

    echo 'Title: ' . $hit['_source']['title'] . '<br>';

    echo 'Content: ';
    if (isset($highlight['content'])) {
        echo implode(' ... ', $highlight['content']);
    } else {
        echo $hit['_source']['content'];
    }

    echo '<hr>';
}