Test for ServerSettings.

serversettings-test.php

<?php

/**
 * @name SSTest
 * @version 1.0.0
 * @main PJZ9n\SSTest\SSTest
 * @api 3.12.0
 */

declare(strict_types=1);

namespace PJZ9n\SSTest;

use pocketmine\event\Listener;
use pocketmine\event\player\PlayerJoinEvent;
use pocketmine\form\Form;
use pocketmine\Player;
use pocketmine\plugin\PluginBase;

class SSTest extends PluginBase implements Listener
{
    public function onEnable(): void
    {
        $this->getServer()->getPluginManager()->registerEvents($this, $this);
    }

    public function onPlayerJoin(PlayerJoinEvent $event): void
    {
        $player = $event->getPlayer();
        $player->setServerSettingsForm(new class implements Form {
            public function handleResponse(Player $player, $data): void
            {
                var_dump($player->getName(), $data);
            }

            public function jsonSerialize(): array
            {
                return [
                    "type" => "custom_form",
                    "icon" => [
                        "type" => "path",
                        "data" => "textures/items/apple",
                    ],
                    "title" => "Settings!",
                    "content" => [
                        [
                            "type" => "label",
                            "text" => "example settings.",
                        ],
                        [
                            "type" => "input",
                            "text" => "Please input.",
                            "default" => date("Y/m/d H:i:s"),
                        ],
                    ],
                ];
            }
        });
    }
}