curl asynchrone pool

$pool = new AsyncPool();

for($i = 0; $i < 10; $i++) {
  $pool->add(function() {
    $ch = curl_init();
    // set url
    curl_setopt($ch,CURLOPT_URL, "http://www.google.com");
    //return the transfer as a string
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    // $output contains the output string
    $output = curl_exec($ch);
    // close curl resource to free up system resources
    curl_close($ch);
    return $output;
  });
}

$result = $pool->execute();

print_r($result);