Ping-Based Device Presence (with Slack webhook)

presence.php

<?php

// timeout in minutes for phone being considered away
// (iphones only check in sporadically to wifi when running on battery)
// can probably lower this and still avoid false positives...
$minutesAway = 21;

date_default_timezone_set("America/Phoenix");

// store everything in an associative array (hacky and simple)
// static DHCP assigned on router for device
$track = array();
$track['ip'] = '192.168.XX.YY';
$track['name'] = 'Matthew';
$track['gone'] = false;
$track['last'] = 0;
$track['timeArrived'] = time();
$track['timeLeft'] = time();
$all[] = $track;

// would put other devices here...


// initial settings when script starts
foreach($all as &$track)
{
	$testNow = Ping($track['ip']);
	$track['gone'] = !$testNow;
}

while(true)
{
	foreach($all as &$track)
	{
		// current status
		$testNow = Ping($track['ip']);

		// debug
		//print "Ping on $track[name]: " . ($testNow ? "YES" : "NO") . "\n";

		// if we've been offline for awhile
		$testGone = !$testNow && time() - $track['last'] > 60 * $minutesAway;

		// did we just leave?
		if($testGone && !$track['gone'])
		{
			print "$track[name] just left\n";
			Send("$track[name] has left the office", "bad");
			$track['timeLeft'] = time();
		}

		// did we just arrive?
		if(!$testGone && $track['gone'])
		{
			print "$track[name] just arrived\n";
			Send("$track[name] has arrived at the office", "good");
			$track['timeArrived'] = time();
		}

		if($testNow)
			$track['last'] = time();

		$track['gone'] = $testGone;

		sleep(1);
	}
}

// this is for OSX!
function Ping($ip)
{
	$str = exec("ping -c 1 -W 1 $ip 2>&1", $input, $result);
	if($result == 0)
		return true;
	else
		return false;
}
	
function Send($text, $color)
{
	// you can specify channel (will use default for webhook otherwise)
	$payload = array(
		//'channel' => '#debug'
		'username' => 'office presence'
		,'icon_emoji' => ":runner:"
		,'attachments' => array(
				array(
					'fallback' => $text
					,'color' => $color
					,'text' => $text
					)
			)
	);

	// your slack webhook goes here!
	$url = 'https://hooks.slack.com/services/YOUR_WEBHOOK_INFO';
	$fields = array(
		'payload' => json_encode($payload)
		);

	$ch = curl_init();
	curl_setopt($ch,CURLOPT_URL, $url);
	curl_setopt($ch,CURLOPT_POST, 1);
	curl_setopt($ch,CURLOPT_POSTFIELDS, $fields);
	$result = curl_exec($ch);
	curl_close($ch);
}