curl asynchrone pool

function curl($url)
{
  $ch = curl_init();
  curl_setopt($ch, CURLOPT_URL, $url);
  curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
  $output = curl_exec($ch);
  curl_close($ch);
  return $output;
}
 
$urls = array(
  'http://www.example.com',
  'http://www.example.co.uk',
  'http://www.example.com.br',
  'http://www.example.ru',
  'http://www.example.es',
);
 
$pool = new Pool(10);
 
foreach ($urls as $url) {
  $pool->submit(new CurlTask($url));
}
 
$pool->shutdown();