Blackfire\Player\Guzzle\RequestFactory::createRequestFromForm PHP Method

    private function createRequestFromForm(Step $step, ValueBag $values, Crawler $crawler = null)
    {
        $selector = $step->getFormSelector();
        $form = $this->language->evaluate($selector, ['_crawler' => $crawler] + $values->all(true));
        if (!count($form)) {
            throw new CrawlException(sprintf('Unable to submit form as button "%s" does not exist.', $selector));
        }
        $formValues = $this->evaluateValues($values, $step->getFormValues());
        $form = $form->form($formValues);
        $headers = $step->getHeaders();
        $body = $this->createBody($values, $form->getValues(), $headers, $step->isJson());
        /*
        // FIXME: when we have files, we need NOT use form_params
        if ($files = $form->getFiles()) {
            foreach ($files as $name => $file) {
                'name' => $name,
                'contents' => $file,
            }
        }
        */
        return new Request($form->getMethod(), $this->fixUri($step, $form->getUri()), $headers, $body);
    }