$bot_url="https://xxxx/conversation_start.php";
$no_answer="Maaf, nanti saya tanyakan ya...";
$message=$event['message'];

$json = file_get_contents($bot_url."?convo_id=&say=".rawurlencode($message['text']));
if($json) {
	$obj = json_decode($json);
    if($obj->botsay!=$no_answer)
    {
        $payload = array(
			'replyToken' => $replyToken,														
			'messages' => array(
						array(
								'type' => 'text',					
								'text' => $obj->botsay
							)
						)
		);
	} else {
		$payload = array(
			'replyToken' => $replyToken,														
			'messages' => array(
							array(
								'type' => 'text',					
								'text' => "Maaf, saya belum bisa jawab"
							)
						)
			);
	}
} else {

//... payload ...

}