Ninjablock PHP presence script

ninja-presence.php

<?php
/**
 * php ninjablock presence driver
 * usage:
 *
 * nohup php -f ninja-presence.php 2>&1 &
 */
include 'nbapi.php';

date_default_timezone_set('CET');
$IPS = ['IP1', 'IP2', '...'];
define( 'ACCESS_TOKEN', 'YOUR ACCESS TOKEN' );
define( 'DEVICE_GUID', 'YOUR STATE DEVICE GUID' );
define( 'CHECK_INTERVAL', 15 ); // seconds
define( 'MISS_THRESHOLD', 3 ); // seconds

$ninja = new Device(ACCESS_TOKEN);

/**
 * check if ip address answers to ping
 * @param $ip ip address to be pinged
 * @return true if ping was successful, false otherwise
 */
function ping($ip) {
	$res = shell_exec("ping -c1 $ip");
	if (strpos($res, '1 received') !== false) {
		return true; // ping successful
	}
	return false;
}

$lastState = $state = false;
$missed = 0;

while (true) {
	$LAST_SEEN = [];
	foreach ($IPS as $ip) {
		if (ping($ip)) {
			$LAST_SEEN[] = $ip;
		}
	}

	// now update status
	$lastState = $state;
	if (count($IPS) === count($LAST_SEEN)) {
		$state = "EverybodyHome";
		$missed = 0;
	} else if (count($LAST_SEEN) > 0) {
		$state = "SomebodyHome";
		$missed = 0;
	} else {
		$missed++;
		if ($missed >= MISS_THRESHOLD) {
			$state = "NobodyHome";
		} else {
			echo "ping missed for $missed times\n";
		} 
	}

	if ($state != $lastState) {
		$ninja->actuate(DEVICE_GUID, array('DA' => $state));
		echo 'presence ' . date('Y-m-d H:i:s') . ': ' . $state . "\n";
	}

	sleep(CHECK_INTERVAL);
}