$pids = array();

$child_pid = pcntl_fork();

if ($child_pid == -1)

{

    throw new Exception( __METHOD__ . "|" . __LINE__ .

            ": fork() error");

}

else if ($child_pid)

{

    //parent

    exit(0);

}

else

{

    //child

    for($i=0;$i<3;$i++)

    {

        $child_pid = pcntl_fork();

        if($child_pid)

        {

            //parent

            $pids[] = $child_pid;

            sleep(5);

            print_r($pids);echo "\n";

        }else{

            //child

            break;

        }

    }

}

while(1)

{

     //your code

    sleep(1);

}