> For the complete documentation index, see [llms.txt](https://docs.roadrunner.dev/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.roadrunner.dev/docs/http/resp-streaming.md).

# Streaming

Response streaming has been available since RoadRunner v2023.3.

RoadRunner supports HTTP response streaming, which allows responses to be sent to the client in chunks. This is useful when you need to send a large amount of data to the client. You don't need to update the configuration to enable this feature; it is enabled by default and controlled by the PHP worker.

## Samples

### Sending a response in chunks

The size of the chunks is controlled by the PHP worker. You can send a chunk by calling the `respond()` method of the `Spiral\RoadRunner\Http\HttpWorker` class. The signature of the method is the following:

{% code title="script.php" %}

```php
    /**
     * @throws \JsonException
     */
    public function respond(int $status, string|Generator $body = '', array $headers = [], bool $endOfStream = true): void
```

{% endcode %}

The `$body` parameter can be a string or a generator. If it is a generator, the worker will iterate over it and send chunks to the client. `$status` and `$headers` are the same as in the `respond()` method of the `Spiral\RoadRunner\Http\HttpWorker` class. The `$endOfStream` parameter indicates whether the response is finished. If set to false, the worker will wait for the next chunk.

Here is an example of a streaming response:

{% code title="worker.php" %}

```php
<?php

require __DIR__ . '/vendor/autoload.php';

use Spiral\RoadRunner;

ini_set('display_errors', 'stderr');
require __DIR__ . "/vendor/autoload.php";

$worker = RoadRunner\Worker::create();
$http = new RoadRunner\Http\HttpWorker($worker);
$read = static function (): Generator {
    foreach (\file(__DIR__ . '/test.txt') as $line) {
        try {
            yield $line;
        } catch (Spiral\RoadRunner\Http\Exception\StreamStoppedException) {
            // Just stop sending data
            return;
        }
    }
};

try {
    while ($req = $http->waitRequest()) {
        $http->respond(200, $read());
    }
} catch (\Throwable $e) {
    $worker->error($e->getMessage());
}
```

{% endcode %}

### Sending headers and status codes

You can send multiple informational responses before the final response. Send an empty body and set `endOfStream: false` for each informational response. Send the final status and headers before streaming its body.

{% hint style="warning" %}
RR ignores worker responses with status `101 Switching Protocols`. A PHP worker cannot upgrade the connection by sending this status. RR also drops bodies attached to informational responses. Do not send informational responses after the final response has started.
{% endhint %}

{% code title="worker.php" %}

```php
<?php

use Spiral\RoadRunner;

ini_set('display_errors', 'stderr');
require __DIR__ . "/vendor/autoload.php";

$worker = RoadRunner\Worker::create();
$http = new RoadRunner\Http\HttpWorker($worker);
$read = static function (): Generator {
    $limit = 10;
    foreach (\file(__DIR__ . '/test.txt') as $line) {
        foreach (explode('"', $line) as $chunk) {
            try {
                usleep(50_000);
                yield $chunk;
            } catch (Spiral\RoadRunner\Http\Exception\StreamStoppedException $e) {
                // Just stop sending data
                return;
            }
            if (--$limit === 0) {
                return;
            }
        }
    }
};


try {
    while ($req = $http->waitRequest()) {
        $http->respond(100, '', headers: ['X-100' => ['100']], endOfStream: false);
        $http->respond(102, '', headers: ['X-102' => ['102']], endOfStream: false);
        $http->respond(103, '', headers: ['Link' => ['</style111.css>; rel=preload; as=style'], 'X-103' => ['103']], endOfStream: false);
        $http->respond(200, $read(), headers: ['X-200' => ['200']], endOfStream: true);
    }
} catch (\Throwable $e) {
    $worker->error($e->getMessage());
}
```

{% endcode %}

This example sends `100`, `102`, and `103` before the final `200` response. Headers supplied only in an informational response are not copied to the final response. Repeat any headers needed in the final `respond()` call.