src/Message.php
public function postback($text, $title, $postback)
    {
        $payload = [
            'template_type' => 'button',
            'text' => $text,
            'buttons' => [
                [
                    'type' => 'postback',
                    'title' => $title,
                    'payload' => $postback
                ]
            ],
        ];

        $this->setAttachment('template', $payload);

        return $this;
    }
public function postback($text, $title, $postback)
    {
        $payload = [
            'template_type' => 'button',
            'text' => $text,
            'buttons' => [
                [
                    'type' => 'postback',
                    'title' => $title,
                    'payload' => $postback
                ]
            ],
        ];

        $this->setAttachment('template', $payload);

        return $this;
    }
Populate simple postback button

@param string $text Text
@param string $title Title
@param string $postback Postback

@return Message