$ch = curl_init();
curl_setopt($ch,CURLOPT_URL,"http://www.example.COM/");
curl_setopt($ch,CURLOPT_HEADER,true);
curl_setopt($ch,CURLOPT_NOBODY,CURLOPT_RETURNtransfer,CURLOPT_FOLLOWLOCATION,CURLOPT_MAXredIRS,10); //follow up to 10 redirections - avoids loops
$data = curl_exec($ch);
curl_close($ch);
if (!$data) {
  echo "Domain Could not be found";
}
else {
  preg_match_all("/HTTP\/1\.[1|0]\s(\d{3})/",$data,$matches);
  $code = end($matches[1]);
  if ($code == 200) {
    echo "Page Found";
  }
  elseif ($code == 404) {
    echo "Page Not Found";
  }
}

来自here的修改版代码.