Bot buttons , how to show them on chat?

[php-wizard]

Thanks for creating this library!

I am trying to show a button to my bot's users (chatting privately with the bot).
But SendMessage has no effect if i try to put a button, no message received on Telegram.
While it works if i send a plain text message.

My code

$replyKeyboardMarkup = ['_' => 'replyKeyboardMarkup', 
		      'resize' => false, 
		      'single_use' => false, 
		      'selective' => false, 
		      'rows' => [	'_' => 'keyboardButtonRow', 'buttons' => [['_' => 'keyboardButton', 'text' => 'testme']]	],
		      'placeholder' => 'Choose an option'];

$replyInlineMarkup = ['_' => 'replyInlineMarkup', 
				'rows' => [
						[	'_' => 'keyboardButtonRow', 
							'buttons' => [
										['_' => 'keyboardButton', 'text' => 'string']
									]
						]
						]
				]; 
$MadelineProto->messages->sendMessage(['peer' => "@$username", 'reply_markup'=>$replyKeyboardMarkup,  'message' => "dummy text", 'parse_mode' => 'HTML' ], ['async' => true]);

$MadelineProto->messages->sendMessage(['peer' => "@$username", 'reply_markup'=>$replyInlineMarkup,  'message' => "dummy text", 'parse_mode' => 'HTML' ], ['async' => true]);
						

What am i missing?
My goal is that when the user clicks the button, i want to launch a command (as if the user typed the command manually).

[php-wizard]

@danog @svdaru Anybody can give me a hint please?

From the logs i see this error: BUTTON_TYPE_INVALID