$this->request

$controllerName = $this->request->getParam('controller' );
$params = $this->request->getAttribute('params' );
$passedArgs = $this->request->getParam('pass' );

// URL is /posts/index?page=1&sort=title
$page = $this->request->getQuery('page' );
$query = $this->request->getQueryParams();

// Input with a name 'MyModel[title]' 
$title = $this->request->getData('MyModel.title' );

$host = $this->request->env('HTTP_HOST' );
$env = $this->request->getServerParams();

// /subdir/articles/edit/1?page=1
$here = $request->getRequestTarget();

$base = $request->getAttribute('base');       //  /subdir
$base = $request->getAttribute('webroot');    //  /subdir/

$jsonData = $this->request->input('json_decode' );
$data = $this->request->input('Cake\Utility\Xml::build' , [ 'return' => 'domdocument' ]);

$this->request->is('post')
$this->request->is('ajax')   // X-Requested-With = XMLHttpRequest
$this->request->is('json')   // application/xml lub text/xml  .json (ext)

$userName = $this->request->session() ->read('Auth.User.name' );

$request->domain();
$request->subdomains();
$request->host();

$request->getMethod();
$this->request->allowMethod([ 'post' , 'delete']);