[PHP] Threading

[Kris]

I want to be able to thread objects .I'm not really sure at all where to start. 
I have an example php script

<?

$a = new sleeper();
$b = new sleeper();
$c = new sleeper();

$a->sleepFor(10);
$b->sleepFor(5);
$c->sleepFor(1);

class sleeper {

 function sleepFor($num) {
  sleep($num);
  echo "sorry I was a sleep for $num \r\n";
 }

}

?>

I want so object $c would print first not last as it is sleeping for less time.
Does that make sense?

Thanks for any help

Kris