private function adjustHeaders($requestType)
    {
        if (! array_key_exists('Accept', $this->headers) && $requestType != 'HEAD') {
            $this->setHeader('Accept', 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8');
        }
        
        if (! array_key_exists('Accept-Language', $this->headers) && $requestType != 'HEAD') {
            $this->setHeader('Accept-Language', 'en-US;q=0.7,en;q=0.3');
        }
        
        if (! array_key_exists('User-Agent', $this->headers) && $requestType != 'HEAD') {
            $this->setHeader('User-Agent', 'phpGenerics 1.0');
        }
        
        if (! array_key_exists('Connection', $this->headers) || strlen($this->headers['Connection']) == 0) {
            $this->adjustConnectionHeader($requestType);
        }
        
        if (! array_key_exists('Accept-Encoding', $this->headers)) {
            if (function_exists('gzinflate')) {
                $encoding = 'gzip, deflate';
            } else {
                $encoding = 'identity';
            }
            $this->setHeader('Accept-Encoding', $encoding);
        }
    }