$queue A queue of middleware entries. * @param callable $resolver Converts a given queue entry to a callable or MiddlewareInterface instance. * * @phpcsSuppress SlevomatCodingStandard.TypeHints.ParameterTypeHint.MissingNativeTypeHint */ public function __construct($queue, ?callable $resolver = null) { if (! is_iterable($queue)) { throw new TypeError('\$queue must be array or Traversable.'); } if (! is_array($queue)) { $queue = iterator_to_array($queue); } if (empty($queue)) { throw new InvalidArgumentException('$queue cannot be empty'); } $this->queue = $queue; if ($resolver === null) { $resolver = function ($entry) { return $entry; }; } $this->resolver = $resolver; } /** * Handles the current entry in the middleware queue and advances. */ abstract public function handle(ServerRequestInterface $request): ResponseInterface; }