摘要：響應準備若不是的對象，則構造成此對象類型本質就是用的類構建響應準備主要是設置響應頭信息類設置編碼格式若傳輸時用分塊編碼，則移除因為采用分塊編碼時可以知道傳輸何時完成

public function prepareResponse($request, $response)
{
    if ($response instanceof PsrResponseInterface) {
        $response = (new HttpFoundationFactory)->createResponse($response);
    }
    // 若不是 SymfonyComponentHttpFoundationSymfonyResponse 的對象，則構造成此對象
    elseif (! $response instanceof SymfonyResponse) {
        $response = new Response($response);
    }

    return $response->prepare($request);
}

public function createResponse(ResponseInterface $psrResponse)
{
    $response = new Response(
        $psrResponse->getBody()->__toString(),
        $psrResponse->getStatusCode(),
        $psrResponse->getHeaders()
    );
    $response->setProtocolVersion($psrResponse->getProtocolVersion());

    foreach ($psrResponse->getHeader("Set-Cookie") as $cookie) {
        $response->headers->setCookie($this->createCookie($cookie));
    }

    return $response;
}

本質就是用的 Response 類

public function __construct($content = "", $status = 200, $headers = array())
{
    $this->headers = new ResponseHeaderBag($headers);
    $this->setContent($content);
    $this->setStatusCode($status);
    $this->setProtocolVersion("1.0");

    // Deprecations
    $class = get_class($this);
    if ($this instanceof PHPUnit_Framework_MockObject_MockObject || $this instanceof ProphecyDoublerDoubleInterface) {
        $class = get_parent_class($class);
    }
    if (isset(self::$deprecationsTriggered[$class])) {
        return;
    }

    self::$deprecationsTriggered[$class] = true;
    foreach (self::$deprecatedMethods as $method) {
        $r = new ReflectionMethod($class, $method);
        if (__CLASS__ !== $r->getDeclaringClass()->getName()) {
            @trigger_error(sprintf("Extending %s::%s() in %s is deprecated since version 3.2 and won"t be supported anymore in 4.0 as it will be final.", __CLASS__, $method, $class), E_USER_DEPRECATED);
        }
    }
}
public function setContent($content)
{
    if (null !== $content && !is_string($content) && !is_numeric($content) && !is_callable(array($content, "__toString"))) {
        throw new UnexpectedValueException(sprintf("The Response content must be a string or object implementing __toString(), "%s" given.", gettype($content)));
    }

    $this->content = (string) $content;

    return $this;
}
public function setStatusCode($code, $text = null)
{
    $this->statusCode = $code = (int) $code;
    if ($this->isInvalid()) {
        throw new InvalidArgumentException(sprintf("The HTTP status code "%s" is not valid.", $code));
    }

    if (null === $text) {
        $this->statusText = isset(self::$statusTexts[$code]) ? self::$statusTexts[$code] : "unknown status";

        return $this;
    }

    if (false === $text) {
        $this->statusText = "";

        return $this;
    }

    $this->statusText = $text;

    return $this;
}
public function isInvalid()
{
    return $this->statusCode < 100 || $this->statusCode >= 600;
}
public function setProtocolVersion($version)
{
    $this->version = $version;

    return $this;
}

主要是設置響應頭

public function prepare(Request $request)
{
    $headers = $this->headers;
    // 信息類
    if ($this->isInformational() || $this->isEmpty()) {
        $this->setContent(null);
        $headers->remove("Content-Type");
        $headers->remove("Content-Length");
    } else {
        if (!$headers->has("Content-Type")) {
            $format = $request->getRequestFormat();
            # static::$formats = array(
            #    "html" => array("text/html", "application/xhtml+xml"),
            #    "txt" => array("text/plain"),
            #    "js" => array("application/javascript", "application/x-javascript", "text/javascript"),
            #    "css" => array("text/css"),
            #    "json" => array("application/json", "application/x-json"),
            #    "xml" => array("text/xml", "application/xml", "application/x-xml"),
            #    "rdf" => array("application/rdf+xml"),
            #    "atom" => array("application/atom+xml"),
            #    "rss" => array("application/rss+xml"),
            #    "form" => array("application/x-www-form-urlencoded"),
            # );
            if (null !== $format && $mimeType = $request->getMimeType($format)) {
                $headers->set("Content-Type", $mimeType);
            }
        }
        // 設置編碼格式
        $charset = $this->charset ?: "UTF-8";
        if (!$headers->has("Content-Type")) {
            $headers->set("Content-Type", "text/html; charset=".$charset);
        } elseif (0 === stripos($headers->get("Content-Type"), "text/") && false === stripos($headers->get("Content-Type"), "charset")) {
            $headers->set("Content-Type", $headers->get("Content-Type")."; charset=".$charset);
        }
        // 若傳輸時用分塊編碼，則移除 Content-Length, 因為采用分塊編碼時可以知道傳輸何時完成
        if ($headers->has("Transfer-Encoding")) {
            $headers->remove("Content-Length");
        }

        if ($request->isMethod("HEAD")) {
            $length = $headers->get("Content-Length");
            $this->setContent(null);
            if ($length) {
                $headers->set("Content-Length", $length);
            }
        }
    }

    if ("HTTP/1.0" != $request->server->get("SERVER_PROTOCOL")) {
        $this->setProtocolVersion("1.1");
    }

    if ("1.0" == $this->getProtocolVersion() && false !== strpos($this->headers->get("Cache-Control"), "no-cache")) {
        $this->headers->set("pragma", "no-cache");
        $this->headers->set("expires", -1);
    }

    $this->ensureIEOverSSLCompatibility($request);

    return $this;
}
public function isInformational()
{
    return $this->statusCode >= 100 && $this->statusCode < 200;
}
protected function ensureIEOverSSLCompatibility(Request $request)
{
    if (false !== stripos($this->headers->get("Content-Disposition"), "attachment") && preg_match("/MSIE (.*?);/i", $request->server->get("HTTP_USER_AGENT"), $match) == 1 && true === $request->isSecure()) {
        if ((int) preg_replace("/(MSIE )(.*?);/", "$2", $match[0]) < 9) {
            $this->headers->remove("Cache-Control");
        }
    }
}