Take and manage ZFS snapshots on Mac OS X 10.5/10.6

*scratch*

#!/usr/bin/php
<?php
print("zfsSnapshot.php : Starting ZFS snapshots\n");

$howFarBackInTime_Hours = 8;
$howFrequentIsScriptCalled_Minutes = 10;
$keepThisMany = $howFarBackInTime_Hours * 60 / $howFrequentIsScriptCalled_Minutes;

print("zfsSnapshot.php : Keeping $keepThisMany snapshots\n");

exec('zfs list -o name -t filesystem | sed 1d', $filesystemList);

foreach ($filesystemList as $filesystem){
    print "Taking snapshot on [$filesystem]\n";
	exec('zfs snapshot "' . $filesystem . '@' . date(DATE_ATOM) . '"');

    $zfsList='zfs list -t snapshot | grep -Eo "' . $filesystem . '@[0-9][0-9][0-9][0-9]-[0-9][0-9]-[0-9][0-9]T[0-9][0-9]:[0-9][0-9]:[0-9][0-9](.[0-9][0-9]:[0-9][0-9])?"';
    exec($zfsList, $snapshotList);
    $numberToDelete=count($snapshotList) - $keepThisMany;

    foreach ($snapshotList as $snapshot){
        if ($numberToDelete > 0){
            print "Deleting old snapshot [" . $snapshot . "]\n";
            print exec('zfs destroy "' . $snapshot . '"');
            $numberToDelete -= 1;
        }
        else break;
    }
    unset($snapshotList);
}
print("zfsSnapshot.php : Finished ZFS snapshots\n\n");
?>