multi thread work?

Hi
how to make a script multi task  based like this

<?


for($i=1;$i<=100;$i++)
{


$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, 'http://www.facebook.com/ajax/reqs.php?__a=1'
);
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_USERAGENT, "Opera/9.80 (Windows NT 5.1; U; tr)
Presto/2.6.22 Version/10.50");
curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
curl_setopt($ch, CURLOPT_REFERER, "http://www.facebook.com/reqs.php");
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
//curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 0);
curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 0);
curl_setopt($ch, CURLOPT_PROXY, "127.0.0.1:8888");
curl_exec($ch);


}
?>


lets say this takes 1000 seconds and it doesnt focus to another curl process
before it finish the previous one

is it possible to let the script focus another curl process without wait
answer of the previous one

i hope if u could understand me ^^