Zend\Diactoros\UploadedFile::getStream PHP Method

    public function getStream()
    {
        if ($this->error !== UPLOAD_ERR_OK) {
            throw new RuntimeException('Cannot retrieve stream due to upload error');
        }
        if ($this->moved) {
            throw new RuntimeException('Cannot retrieve stream after it has already been moved');
        }
        if ($this->stream instanceof StreamInterface) {
            return $this->stream;
        }
        $this->stream = new Stream($this->file);
        return $this->stream;
    }