Aerys\Http1Driver::writer PHP Method

    public function writer(InternalRequest $ireq) : \Generator
    {
        $headers = yield;
        $client = $ireq->client;
        if (!empty($headers["connection"])) {
            foreach ($headers["connection"] as $connection) {
                if (\strcasecmp($connection, "close") === 0) {
                    $client->shouldClose = true;
                }
            }
        }
        $lines = ["HTTP/{$ireq->protocol} {$headers[":status"]} {$headers[":reason"]}"];
        unset($headers[":status"], $headers[":reason"]);
        foreach ($headers as $headerField => $headerLines) {
            if ($headerField[0] !== ":") {
                foreach ($headerLines as $headerLine) {
                    /* verify header fields (per RFC) and header values against containing \n */
                    \assert(strpbrk($headerField, "\n\t ()<>@,;:\\\"/[]?={}") === false && strpbrk($headerLine, "\n") === false);
                    $lines[] = "{$headerField}: {$headerLine}";
                }
            }
        }
        $lines[] = "\r\n";
        $msgPart = \implode("\r\n", $lines);
        $msgs = "";
        do {
            $msgs .= $msgPart;
            if ($msgPart === false || \strlen($msgs) >= $client->options->outputBufferSize) {
                $client->writeBuffer .= $msgs;
                ($this->responseWriter)($client);
                $msgs = "";
                if ($client->isDead & Client::CLOSED_WR) {
                    if (!$client->bufferPromisor) {
                        $client->bufferPromisor = new Deferred();
                        $client->bufferPromisor->fail(new ClientException());
                    }
                    while (true) {
                        yield;
                    }
                }
                $client->bufferSize = \strlen($client->writeBuffer);
                if ($client->bufferPromisor) {
                    if ($client->bufferSize <= $client->options->softStreamCap) {
                        $client->bufferPromisor->succeed();
                    }
                } elseif ($client->bufferSize > $client->options->softStreamCap) {
                    $client->bufferPromisor = new Deferred();
                }
            }
        } while (($msgPart = yield) !== null);
        $client->writeBuffer .= $msgs;
        // parserEmitLock check is required to prevent recursive continuation of the parser
        if ($client->requestParser && $client->parserEmitLock && !$client->shouldClose) {
            $client->requestParser->send(false);
        }
        ($this->responseWriter)($client, $final = true);
        if ($client->isDead & Client::CLOSED_WR) {
            if (!$client->bufferPromisor) {
                $client->bufferPromisor = new Deferred();
                $client->bufferPromisor->fail(new ClientException());
            }
        } elseif ($client->isDead & Client::CLOSED_RD && $client->bodyPromisors) {
            array_pop($client->bodyPromisors)->fail(new ClientException());
            // just one element with Http1Driver
        }
    }