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Controller
Symfony2 – Franz Jordán 2011
A controller is a PHP function you create that takes information from the HTTP request and
constructs and returns an HTTP response (as a Symfony2 Response object). The response could
be an HTML page, an XML document, a serialized JSON array, an image, a redirect, a 404 error or
anything else you can dream up. The controller contains whatever arbitrary logic your
applicationneeds to render the content of a page.
To see how simple this is, let's look at a Symfony2 controller in action. The following controller
would render a page that simply prints Hello world!:
use Symfony\Component\HttpFoundation\Response;
public function helloAction()
{
return new Response('Hello world!');
}
The goal of a controller is always the same: create and return a Response object. Along the
way, it might read information from the request, load a database resource, send an email, or set
information on the user's session. But in all cases, the controller will eventually return
the Responseobject that will be delivered back to the client.
There's no magic and no other requirements to worry about! Here are a few common examples:
Controller A prepares a Response object representing the content for the homepage of
the site.
Controller B reads the slug parameter from the request to load a blog entry from the
database and create a Response object displaying that blog. If the slug can't be found
in the database, it creates and returns a Response object with a 404 status code.
Controller C handles the form submission of a contact form. It reads the form information
from the request, saves the contact information to the database and emails the contact
information to the webmaster. Finally, it creates a Response object that redirects the
client's browser to the contact form "thank you" page.
Requests, Controller, Response Lifecycle
Every request handled by a Symfony2 project goes through the same simple lifecycle. The
framework takes care of the repetitive tasks and ultimately executes a controller, which houses
your custom application code:
1. Each request is handled by a single front controller file (e.g. app.php or app_dev.php)
that's bootstraps the application;
2. The Router reads information from the request (e.g. the URI), finds a route that matches
that information, and reads the _controller parameter from the route;
3. The controller from the matched route is executed and the code inside the controller
creates and returns a Response object;
4. The HTTP headers and content of the Response object are sent back to the client.
Creating a page is as easy as creating a controller (#3) and making a route that maps a URL to
that controller (#2).
Though similarly named, a "front controller" is different from the "controllers" we'll talk about in
this chapter. A front controller is a short PHP file that lives in your web directory and through
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