check proxy

function check_proxy($proxy) {
  $ch = curl_init();
  curl_setopt($ch,CURLOPT_PROXY,$proxy);
  curl_setopt($ch,CURLOPT_URL,"http://www.google.com");
  curl_setopt($ch,CURLOPT_RETURNTRANSFER,1);
  $result = curl_exec($ch);
  $http_code = curl_getinfo($ch,CURLINFO_HTTP_CODE);
  curl_close($ch);
  if ($http_code>=200 && $http_code<300) {
    return true;
  } else {
    return false;
  }
}