protected function outputUploadOutcome()
    {
        $json = new \stdClass();
        // errors
        if(!$this->uploadOk) {
            if($this->uploader->getMessages()) {
                $this->uploadMessages[] = implode('\n', $this->uploader->getMessages());
            }
            $json->error = implode('\n', $this->uploadMessages);
            $this->httpResponse = $this->httpResponse->withStatus('412', $json->error);
        } else {
            //input file informations
            $json->input = [
                'name' => $this->uploadFields[$this->uploadedField]->getInputFile(),
                'hash' => $this->uploadFields[$this->uploadedField]->getInputHash()
            ];
            // generated file(s) paths
            $json->outputs = $this->uploadFields[$this->uploadedField]->getOutputsFiles();
        }
        return json_encode($json);
    }