protected function processPostFields()
    {
        if (!$this->postFiles) {
            $this->removeHeader('Expect')->setHeader('Content-Type', self::URL_ENCODED);
        } else {
            $this->setHeader('Content-Type', self::MULTIPART);
            if ($this->expectCutoff !== false) {
                $this->setHeader('Expect', '100-Continue');
            }
        }
    }