<?php
declare(strict_types=1);

use AdrHumphreys\TextDropdownField\TextDropdownField;
use SilverStripe\ORM\DataObject;

class Example extends DataObject
{
    /**
     * @var string[]
     */
    private static $db = [
        'TextContent' => 'Varchar(20)',
        'DropdownContent' => 'Varchar(20)',
    ];

    public function getCMSFields()
    {
        $fields = parent::getCMSFields();

        $source = [
            'p' => 'Paragraph',
            'h1' => 'Header 1',
            'h2' => 'Header 2',
        ];

        $fields->addFieldToTab(
            'Root.Main',
            TextDropdownField::create(
                'NameThatDoesntMatter',
                'Title',
                'TextContent',
                'DropdownContent',
                $source
        ));

        return $fields;
    }
}