You can rewrite your entire variable section and constructor with PHP 8 constructor promotion:
class PostController extends BaseController
/** Description */
public function __construct(protected PostForm $postForm,
protected PostCreationService $post,
protected PostRepository $...
You didn't tell us what kind of application you maintain but when it's something with a UI then you shouldn't need this kind of validation at all. Instead you should use proper masks for the input fields and prevent users from entering wrong characters entriely.