<?php

$access_token = '...';
$api = 'https://api.telegram.org/bot' . $access_token;


$output = json_decode(file_get_contents('php://input'), TRUE);
$chat_id = $output['message']['chat']['id'];
$first_name = $output['message']['chat']['first_name'];
$message = $output['message']['text'];
switch($message) {
 case '/test':
    sendMessage($chat_id, "Вы уверены?");
    break;
    default:
    $sorry_text =  $first_name . ' , мне нечего ответить';
    sendMessage($chat_id, $sorry_text);
}
function sendMessage($chat_id, $message, $encodedMarkup) {
  file_get_contents($GLOBALS['api'] . '/sendMessage?chat_id=' . $chat_id . '&text=' . urlencode($message) . $encodedMarkup);
}

$x1 = array("text"=>"First Button","callback_data"=>"test1");
$x2 = array("text"=>"Second Button","callback_data"=>"test2");
$opz = [[$x1,$x2]];
$keyboard=array("inline_keyboard"=>$opz);
$keyboard = json_encode($keyboard);
      sendMessage($chat_id, "testt2", $keyboard);
      break;

<?php
$access_token = 'xxx';
$api = 'https://api.telegram.org/bot' . $access_token;
$output = json_decode(file_get_contents('php://input'), TRUE);
$chat_id = $output['message']['chat']['id'];
$first_name = $output['message']['chat']['first_name'];
$message = $output['message']['text'];
$callback_query = $output['callback_query'];
$data = $callback_query['data'];
$message_id = ['callback_query']['message']['message_id'];
$chat_id_in = $callback_query['message']['chat']['id'];
switch($message) {
    case '/test':
    $inline_button1 = array("text"=>"Google url","url"=>"http://google.com");
    $inline_button2 = array("text"=>"work plz","callback_data"=>'/plz');
    $inline_keyboard = [[$inline_button1,$inline_button2]];
    $keyboard=array("inline_keyboard"=>$inline_keyboard);
    $replyMarkup = json_encode($keyboard);
     sendMessage($chat_id, "ok", $replyMarkup);
    break;
}
switch($data){
    case '/plz':
    sendMessage($chat_id_in, "plz");
    break;
}
function sendMessage($chat_id, $message, $replyMarkup) {
  file_get_contents($GLOBALS['api'] . '/sendMessage?chat_id=' . $chat_id . '&text=' . urlencode($message) . '&reply_markup=' . $replyMarkup);
}