example mattermost bot using an outgoing webhook and incoming webhooks.

xerxes_mattermost.php

<?php

//Example Xerxes mattermost bot with incoming/outgoing webhook use.
error_reporting(E_ERROR | E_WARNING | E_PARSE);

//function to send the message payload to mattermost.
function send_to_mattermost($message) {

    global $channel;

    $mattermost_server = '';
    $icon_url = 'http://i.imgur.com/f16pg.jpg';

    $payload = 'payload=' . json_encode(array('username' => 'BESTBOT', 'icon_url' => $icon_url, 'text' => $message));

    $ch = curl_init();

    curl_setopt($ch, CURLOPT_URL,"https://" . $mattermost_server . "/hooks/" . $channel);
    curl_setopt($ch, CURLOPT_POST, 1);
    curl_setopt($ch, CURLOPT_POSTFIELDS, $payload);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

    $server_output = curl_exec ($ch);

    curl_close ($ch);

}

//get our posted json from mattermost
$post = file_get_contents("php://input");
$input = json_decode($post,true);

//grab the bits we need
$message = $input['text'];
$user = $input['user_name'];
$channel = $input['channel_name'];

//if statement to map the channel name to the incoming webhook to use. 
if ($channel == 'ops-chat') {

    $channel = 'sjk87hwt3fdfdxkuq5kkw3argc';

} elseif ($channel == 'off-topic') {

    $channel = '7lamncptxqesr3joakfkbtxdrbi'

} else {

    exit();

}

//match for commands starting with ?, else don't go any further.
if (!preg_match("/^\?/", $message)) { exit(0); }

//split the incoming text into the command and arguments. 
$input = $message;
$nick = $user;
$toks = explode(" ",$input);
$command = str_replace("?","",$toks[0]);
$arg1 = $toks[1];
$arg2 = $toks[2];
$arg3 = $toks[3];

//functions for our commands.

function excuse() {

    $msg = file_get_contents("http://pages.cs.wisc.edu/~ballard/bofh/excuses");
    $msg = explode(PHP_EOL, $msg);
    $msg = $msg[array_rand($msg, 1)];

    return $msg;

}

function coding_love () {

    $url = file_get_contents("http://thecodinglove.com/random");
    preg_match_all('/<div class="centre"> <h.*/', $url, $matches);

    if (isset($matches[0][0])) {

        $matches = explode('<p', $matches[0][0]);

        $title = explode('<h3>', $matches[0]);
        $title = explode('</h3>', $title[1]);
        $title = trim($title[0]);

        $title = str_replace('&rsquo;', "'", $title);
        $title = str_replace('&ldquo;', '"', $title);
        $title = str_replace('&rdquo;', '"', $title);
        $title = str_replace('&hellip;', '...', $title);

        preg_match_all('/http.*.(gif|jpg)/', $matches[1], $matches2);

        $img = trim($matches2[0][0]);

        if (!preg_match('/minus/', $img)) {

            if (preg_match('/.jpg$/', $img)) {

                $img = preg_replace('/.jpg$/', '.gif', $img);

            }

            send_to_mattermost($title . PHP_EOL . $img);

        }

    }

}

function random_password($length = 16) {
    $chars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789!@#$%^&*()_-=+;:,.?";
    $password = substr(str_shuffle($chars),0,$length);
    return $password;
}

//action the relevant output per command.
switch(strtolower($command)){

    case 'sleep':
        send_to_mattermost("zzZzzZzzzZzzz!");
    break;

    case 'bark':
        send_to_mattermost("WOOF!");
    break;

    case 'hello':
        send_to_mattermost("Hello " . $nick . "!");
    break;

    case 'flashbang':
        send_to_mattermost('Counter-Terrorists Win');
    break;

    case 'excuse':
        send_to_mattermost(excuse());
    break;

    case 'code':
        coding_love();
    break;

    case 'joke':
        $joke = json_decode(file_get_contents('http://tambal.azurewebsites.net/joke/random'),1);
        send_to_mattermost($joke['joke']);
    break;

    case 'password':
        if (isset($arg1)) {
            $length = intval($arg1);
            send_to_mattermost(random_password($length));
        } else {
            send_to_mattermost(random_password());
        }
    break;

    case 'xkcd':
        $num = json_decode(file_get_contents("http://xkcd.com/info.0.json"),true);
        $num = $num['num'];
        $comic_num = mt_rand(0, $num);
        $comic_array = json_decode(file_get_contents("http://xkcd.com/" . $comic_num . "/info.0.json"),true);
        $comic_img = $comic_array['img'];
        $comic_alt = $comic_array['alt'];

        send_to_mattermost($comic_img . PHP_EOL . $comic_alt);
    break;

    default:
        send_to_mattermost("I'm sorry, " . $nick . ". I'm afraid I can't " . $command . " because; " . excuse());
    break;

}

exit;