TYPO3 PageTitleProvider for own extensions

Procedure:

Create a class MyPageTitleProvider.php in myextension/Classes/PageTitle:

<?php
namespace Rms\Blog;
use TYPO3\CMS\Core\PageTitle\AbstractPageTitleProvider;
class MyPageTitleProvider extends AbstractPageTitleProvider
{
    /**
     * @param string $title
     */
    public function setTitle(string $title)
    {
        $this->title = $title;
    }
}

After that, the PageTitleProvider and, if there are several providers, the priority are configured in TypoScript

config.pageTitleProviders { 
    custom {
        provider = Rms\Blog\MyPageTitleProvider
        before = pages
        after = altPageTitle
    }
}

Now the new PageTitleProvider can be used e.g. inside a show() function to override the default page title:

<?php
class PostController extends \TYPO3\CMS\Extbase\Mvc\Controller\ActionController
{
    /**
     * action show
     *
     * @param \Rms\Blog\Domain\Model\Post $post
     * @return \Psr\Http\Message\ResponseInterface
     */
    public function showAction(\Rms\Blog\Domain\Model\Post $post): \Psr\Http\Message\ResponseInterface
    {
        $titleProvider = GeneralUtility::makeInstance(\Rms\Blog\MyPageTitleProvider::class);
        $titleProvider->setTitle($post->getTitle());

        $this->view->assign('post', $post);
        return $this->htmlResponse();
    }
}