How to Make PHP Generate Chunked Response

Transfer-Encoding: chunked header in PHP. What is padding for?

The padding is for filling the server buffer, as I understand.

Without it the server will wait until PHP will fill it and after this will flush it - even if in PHP code you do flush().

PHP Output buffer flush issue on Apache/Linux (May 2010; on Server Fault)

Transfer-Encoding: chunked sent twice (chunk size included in response body)

As @Joe pointed out before, that is the normal behavior when Chunked transfer enconding is enabled. My tests where not accurate because I was requesting Apache directly on the server. Actually, when I was experiencing the problem in Chrome I was querying a Nginx service as a proxy for Apache.

By running tcpdump I realized that Nginx was rechunking responses, but only when rewritting HTTP status header (header('HTTP/1.1 200 OK')) in PHP. The solution to sending Transfer-Encoding: chunked twice is to set chunked_transfer_encoding off in the location context of my Nginx .php handler.

How can I use chunked transfer encoding in Laravel?

In my specific case I've solved my problem by using this code(example):

use Symfony\Component\HttpFoundation\StreamedResponse;

$response = new StreamedResponse();
$response->setCallback(function () {
    var_dump('Hello World');
    flush();
    sleep(2);
    var_dump('Hello World');
    flush();
});
$response->send();

POST request to PHP7 with chunked encoding does not properly return result

It is/was a bug in PHP7 which was fixed very recently with https://github.com/php/php-src/pull/1745 . It is not yet within any official release but eventually will end up there some time.

Before the above PR, a bug was also reported describing a similar issue: https://bugs.php.net/bug.php?id=71466

know when data chunk transfer is closed

By calling connection_aborted() you can find out if the client is still connected or not. This could be done within your for loop like below.

Also you will need to tell PHP to continue execution after the client disconnects by calling ignore_user_abort(). If you don't do that, your script will terminate as soon as the client disconnects. Depending on your PHP config, you may also need to set a larger or unlimited time limit using set_time_limit().

ignore_user_abort(true);

for ($i = 0; $i < 10000; $i++) {

     if(connection_aborted()){
         // client disconnected, write to file here
     }

     echo "string";
     ob_flush();
     flush();
     sleep(2);
}