if($userMessage == "send image"){ //your message
$imageMessage = new \LINE\LINEBot\MessageBuilder\ImageMessageBuilder("https://myanimelist.cdn-dena.com/images/characters/8/320273.jpg","https://myanimelist.cdn-dena.com/images/characters/8/320273.jpg");
$result = $bot->replyMessage($event['replyToken'], $imageMessage);
return $result->getHTTPStatus() . ' ' . $result->getRawBody();
}