proc_open, proc_get_status, proc_close

Hello,
with the code below, $rv is 0 :-)

--- begin code ---
$pdesc=[0=>['pipe','r'],1=>['file','stdout.log','w'],2=>['file','stderr.log','w']];
$proc=proc_open('sleep 3',$pdesc,$pipes);
fclose($pipes[0]);
$rv=proc_close($proc);
echo('rv: '.$rv.PHP_EOL);
exit(0);
--- end code ---

With the code below, $rv is -1 :-(

--- begin code ---
$pdesc=[0=>['pipe','r'],1=>['file','stdout.log','w'],2=>['file',stderr.log','w']];
$proc=proc_open('sleep 3',$pdesc,$pipes);
$done=false;
while ($done===false) {
	$pstat=proc_get_status($proc);
	if (!$pstat['running']) $done=true;
	usleep(500000);
}
fclose($pipes[0]);
$rv=proc_close($proc);
echo('rv: '.$rv.PHP_EOL);
exit(0);
--- end code ---

Why oh why?