php pcntl 多进程学习

declare(ticks=1);

pcntl_signal(SIGCHLD, "sig_handler");
function sig_handler($signo)
{
switch ($signo) {
case SIGCHLD:
$status = 0;
$child_id = pcntl_wait($status);
echo sprintf("child exit id: {$child_id} \n");
exit(0);
break;

default:
echo 'uncaugh signal !';
}

}

$pid = pcntl_fork();
if($pid>0)
{
echo sprintf("fork child id: {$pid} \n");

while(1){
sleep(1);
}

}else{
echo "child exit \n";
}