$tg = new Telegram\Client("___BOT_API_SECRET___");

$tg->performSingleMethod(new Telegram\Method\SetWebhookInfo("http://example.com/handler.php"));

$tg->onMessage(function(Telegram\Client $tg, Telegram\Model\Message $message) {
    $fromUserId = $message->getFrom()->getId();
    // do something...
);

$reply = new Telegram\Method\SendMessage($toId, $text);
$tg->performSingleMethod($reply);

$tg->onMessage(function(Telegram\Client $tg, Telegram\Model\Message $message) {
    
    $reply = new Telegram\Method\SendMessage($message->getChatId());
    
    $text = getSomeText(); // TODO
    $reply->setText($text);
 
    // If need, we can set parse mode - markdown or html   
    $reply->setParseMode(ParseMode::MARKDOWN);
    
    $tg->performHookMethod($reply);
    exit; // prevent output unnecessary data and stop script
});

use Telegram\Model\Keyboard\InlineKeyboard;
use Telegram\Model\Keyboard\InlineKeyboardButton;
use Telegram\Method\SendMessage;

// ...

// create keyboard
$keyboard = new InlineKeyboard;

// create row in keyboard
$row = $keyboard->addRow();

// create button
$button = new InlineKeyboardButton("Awesome button");
// set callback data
$button->setCallback("sayHello");

// create message
$reply = new SendMessage($message->getChatId());
// set text
$reply->setText("Click on button below");
// set keyboard in message
$reply->setReplyMarkup($keyboard);
// send message
$tg->performSingleMethod($reply);

$tg->onCallbackQuery(function(Telegram\Client $tg, Telegram\Model\Response\CallbackQuery $query) {
    if ($query->getData() === "sayHello") {
        $upd = new EditMessageText(
            $query->getChatId(),
            $query->getMessageId());
            
        $upd->setText("Hello, world!");
        
        $tg->performHookMethod($upd);
    }
});