gistfile1.php

#!/usr/bin/php
<?php

$cmd = "/usr/lib/update-notifier/update-motd-reboot-required";

$out = array();

$returnvar = 0;

$return = exec($cmd, $out, $returnvar);

if($returnvar != 0)
{
        echo "UNKNOWN: Error retrieving reboot status";
        exit(3);
}

if($return == "*** System restart required ***")
{
        echo "WARNING: *** System restart required ***\n";
        exit(1);
}

echo "OK\n";
exit(0);