Psr7Middlewares\Middleware\FormatNegotiator::getFormat PHP Method

    public static function getFormat(ServerRequestInterface $request)
    {
        return self::getAttribute($request, self::KEY);
    }

 /**
  * Execute the middleware.
  *
  * @param ServerRequestInterface $request
  * @param ResponseInterface      $response
  * @param callable               $next
  *
  * @return ResponseInterface
  */
 public function __invoke(ServerRequestInterface $request, ResponseInterface $response, callable $next)
 {
     if (!Middleware::hasAttribute($request, FormatNegotiator::KEY)) {
         throw new RuntimeException('Csrf middleware needs FormatNegotiator executed before');
     }
     if (!Middleware::hasAttribute($request, ClientIp::KEY)) {
         throw new RuntimeException('Csrf middleware needs ClientIp executed before');
     }
     if ($this->storage === null) {
         if (session_status() !== PHP_SESSION_ACTIVE) {
             throw new RuntimeException('Csrf middleware needs an active php session or a storage defined');
         }
         if (!isset($_SESSION[$this->sessionIndex])) {
             $_SESSION[$this->sessionIndex] = [];
         }
         $this->storage =& $_SESSION[$this->sessionIndex];
     }
     if (FormatNegotiator::getFormat($request) !== 'html') {
         return $next($request, $response);
     }
     if (Utils\Helpers::isPost($request) && !$this->validateRequest($request)) {
         return $response->withStatus(403);
     }
     $response = $next($request, $response);
     return $this->insertIntoPostForms($response, function ($match) use($request) {
         preg_match('/action=["\']?([^"\'\\s]+)["\']?/i', $match[0], $matches);
         $action = empty($matches[1]) ? $request->getUri()->getPath() : $matches[1];
         return $match[0] . $this->generateTokens($request, $action);
     });
 }