<?php

    namespace your\name\space;

    use pocketmine\form\Form;
    use pocketmine\Player;

    class ExampleForm implements Form
    {

        public function jsonSerialize(): array
        {
            return [
                "type" => "form",
                "title" => "タイトル",
                "content" => "コンテンツ1\nコンテンツ2",
                "buttons" => [
                    [
                        "text" => "ボタン1",
                    ],
                    [
                        "text" => "ボタン2",
                    ],
                    [
                        "text" => "ボタン3",
                    ],
                    [
                        "text" => "ボタン4",
                    ],
                ],
            ];
        }

        public function handleResponse(Player $player, $data): void
        {
            if ($data === null) {
                return;
            }
            switch ($data) {
                case 0:
                    //ボタン1
                    break;
                case 1:
                    //ボタン2
                    break;
                case 2:
                    //ボタン3
                    break;
                case 3:
                    //ボタン4
                    break;
            }
        }

    }