/* 
* 类用途: 实现类似于asp中的response功能 
*/
final class Response { 
  private $headers = array();  
  private $output; 
  private $level = 0; 
  public function addHeader($key, $value) { 
    $this->headers[$key] = $value; 
  } 
  public function removeHeader($key) { 
    if (isset($this->headers[$key])) { 
      unset($this->headers[$key]); 
    } 
  } 
  public function redirect($url) { 
    header('Location: ' . $url); 
    exit; 
  } 
  public function setOutput($output, $level = 0) { 
    $this->output = $output; 
    $this->level = $level; 
  } 
  private function compress($data, $level = 0) { 
    if (isset($_SERVER['HTTP_ACCEPT_ENCODING']) && (strpos($_SERVER['HTTP_ACCEPT_ENCODING'], 'gzip') !== FALSE)) { 
      $encoding = 'gzip'; 
    }  
    if (isset($_SERVER['HTTP_ACCEPT_ENCODING']) && (strpos($_SERVER['HTTP_ACCEPT_ENCODING'], 'x-gzip') !== FALSE)) { 
      $encoding = 'x-gzip'; 
    } 
    if (!isset($encoding)) { 
      return $data; 
    } 
    if (!extension_loaded('zlib') || ini_get('zlib.output_compression')) { 
      return $data; 
    } 
    if (headers_sent()) { 
      return $data; 
    } 
    if (connection_status()) {  
      return $data; 
    } 
    $this->addHeader('Content-Encoding', $encoding); 
    return gzencode($data, (int)$level); 
  } 
  public function output() { 
    if ($this->level) { 
      $ouput = $this->compress($this->output, $this->level); 
    } else { 
      $ouput = $this->output; 
    }   
    if (!headers_sent()) { 
      foreach ($this->headers as $key => $value) { 
        header($key . ': ' . $value); 
      } 
    } 
    echo $ouput; 
  } 
}