Lets say we want to build a paginated list of products, where the number of the page is passed as a query string parameter. For instance, to fetch the 3rd page, you'd go to:

http://example.com/products?page=3

The raw HTTP request would look something like this:

GET /products?page=3 HTTP/1.1
Host: example.com
Accept: text/html
User-Agent: Mozilla/5.0 (Macintosh)

In order to get the page number from the request object, you can access the query property:

$page = $request->query->get('page'); // 3

In the case of a page parameter, you will probably want to pass a default value in case the query string parameter is not set:

$page = $request->query->get('page', 1);

This means that when someone visits http://example.com/products (note the absence of the query string), the $page variable will contain the default value 1.

PHP exposes a number of so-called global variables which contain information about the HTTP request, such as $_POST, $_GET, $_FILES, $_SESSION, etc. The Request class contains a static createFromGlobals() method in order to instantiate a request object based on these variables:

use Symfony\Component\HttpFoundation\Request;

$request = Request::createFromGlobals();

When using the Symfony framework, you should not instantiate the request object yourself. Instead, you should use the object that is instantiated when the framework is bootstrapped in app.php / app_dev.php. For instance by type hinting the request object in your controller.

To get the contents of a form that is submitted with method="post", use the post property:

$name = $request->request->get('name');

$id = $request->cookies->get('PHPSESSID');

This will return the value of the 'PHPSESSID' cookie sent by the browser.