Returning Responses

Part of the HTTP cycle is return responses to the clients. Phalcon\HTTP\Response is the Phalcon component designed to achieve this task. HTTP responses are usually composed by headers and body. The basic usage is the following:

<?php

// Getting a response instance
$response = new \Phalcon\Http\Response();

//Set status code
$response->setRawHeader(404, "Not Found");

//Set the content of the response
$response->setContent("Sorry, the page doesn't exist");

//Send response to the client
$response->send();

Keep in mind that if you’re using the full MVC stack there is no need to create responses manually. However, if you need to return a responde directly from a controller’s action follow this example:

<?php

class FeedController extends Phalcon\Mvc\Controller
{

    public function getAction()
    {
        // Getting a response instance
        $response = new \Phalcon\Http\Request();

        $feed = //.. load here the feed

        //Set the content of the response
        $response->setContent($feed->asString());

        //Return the response
        return $response;
    }

}

Working with Headers

Headers are an important part of the whole HTTP response. It contains useful information about the response state like the HTTP status, type of response and much more.

You can set headers in the following way:

<?php

//Setting it by its name
$response->setHeader("Content-Type", "application/pdf");
$response->setHeader("Content-Disposition", 'attachment; filename="downloaded.pdf"');

//Setting a raw header
$response->setRawHeader("HTTP/1.1 200 OK");

A Phalcon\HTTP\Response\Headers bag internally manages headers. This class allows to manage headers before sending it to client:

<?php

//Get the headers bag
$headers = $response->getHeaders();

//Get a header by its name
$contentType = $response->getHeaders()->get("Content-Type");

Making Redirections

With Phalcon\HTTP\Response you can also make HTTP redirections:

<?php

//Making a redirection to the default URI
$response->redirect();

//Making a redirection using the local base URI
$response->redirect("posts/index");

//Making a redirection to an external URL
$response->redirect("http://en.wikipedia.org", true);

//Making a redirection specifyng the HTTP status code
$response->redirect("http://www.example.com/new-location", true, 301);

All internal URIs are generated using the ‘url’ service (by default Phalcon\Mvc\Url), in this way you can make redirections based on the routes you’ve currently defined in the application:

<?php

//Making a redirection based on a named route
$response->redirect(array(
    "for" => "index-lang",
    "lang" => "jp",
    "controller" => "index"
));

Note that making a redirection doesn’t disable the view component, so if there is a view asociated with the current action it will be executed anyway. You can disable the view from a controller by executing $this->view->disable();

HTTP Cache

One of the easiest ways to improve the performance in your applications also reducing the traffic is the HTTP Cache. Most modern browsers support HTTP caching and is one of the reasons why many websites are currently fast.

The secret are the headers sent by the application when serving a page for the first time, these headers are:

• Expires: With this header the application can set a date in the future or the past telling the browser when the page must expire.
• Cache-Control: This header allows to specify how much time a page should be considered fresh in the browser.
• Last-Modified: This header tells the browser which was the last time the site was updated avoiding page re-loads
• ETag: An etag is a unique identifier that must be created including the modification timestamp of the current page

Setting an Expiration Time

The expiration date is one of the most easy and effective ways to cache a page in the client (browser). Starting from the current date we add over time, then, this will maintain the page stored in the browser cache until this date expires without requesting the content to the server again:

<?php

$expireDate = new DateTime();
$expireDate->modify('+2 months');

$response->setExpires($expireDate);

The Response component automatically shows the date in GMT timezone in order as is expected in an Expires header.

Moreover if we set a date in the past this will tell the browser to always refresh the requested page:

<?php

$expireDate = new DateTime();
$expireDate->modify('-10 minutes');

$response->setExpires($expireDate);

Browsers relies on the client’s clock to assess if this date has passed or not, the client clock can be modified to make pages expire, this may represent a limitation for this cache mechanism.

Cache-Control

This header provides a safer way to cache the pages served. We simply must specify a time in seconds telling the browser how much time it must keep the page in its cache:

<?php

//Starting from now, cache the page for one day
$response->setHeader('Cache-Control', 'max-age=86400');

The opposite effect (avoid page caching) is achieved in this way:

<?php

//Never cache the served page
$response->setHeader('Cache-Control', 'private, max-age=0, must-revalidate');

E-Tag

A “entity-tag” or “E-tag” is a unique identifier that helps the browser to realize if the page has changed or not between two requests. The identifier must be calculated taking into account that this must change if the content has changed previously served:

<?php

//Calculate the E-Tag based on the modification time of the latest news
$recentDate = News::maximum(array('column' => 'created_at'));
$eTag = md5($recentDate);

//Send a E-Tag header
$response->setHeader('E-Tag', $eTag);