/* 
* 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; 
 } 
}