Used this script to verify that passing `0` and `0.999321` (for example) have the same effect to `stream_select()`:
<?php
$spec = array(
0 => array('pipe', 'r'),
1 => array('pipe', 'w'),
2 => array('pipe', 'w'),
);
$pipes = array();
$proc = proc_open('sleep 30', $spec, $pipes);
list($stdin, $stdout, $stderr) = $pipes;
$read = array($stdout, $stderr);
$write = array();
$except = array();
$select_start = microtime(true);
stream_select($read, $write, $except, 0.999321, 80000);
$select_end = microtime(true);
printf(
"select() took %d us to return.\n",
($select_end - $select_start) * 1000000);