Very useful when making daemons, for example:
<?php
$pid = pcntl_fork(); // fork
if ($pid < 0)
exit;
else if ($pid) // parent
exit;
else { // child
$sid = posix_setsid();
if ($sid < 0)
exit;
for($i = 0; $i <= 60; $i++) { // do something for 5 minutes
sleep(5);
}
}
?>