PHP Final Property redeclaration as non-final

articles.php

<?php
class Article {
    private final $comments = [];
    public function addComment(Comment $comment) {
        $this->comments[] = $comment;
    }
    public function clearComments() {
        $this->comments = [];
    }
}
class ExtendedArticle extends Article {
    private $comments = [];
}
class Comment {}

$article = new Article();
$article->addComment(new Comment());
$article->addComment(new Comment());
$article->clearComments(); 
//Warning: Cannot change final property: Article::$comments which has already defined value in articles.php on line 8
var_dump($article);
//object(Article)#1 (1) {
//  ["comments":"Article":private]=>
//  array(2) {
//    [0]=>
//    object(Comment)#2 (0) {
//    }
//    [1]=>
//    object(Comment)#3 (0) {
//    }
//  }
//}

$extendedArticle = new ExtendedArticle();
$extendedArticle->addComment(new Comment());
$extendedArticle->addComment(new Comment());
var_dump($extendedArticle);
//object(ExtendedArticle)#4 (2) {
//  ["comments":"ExtendedArticle":private]=>
//  array(0) {
//  }
//  ["comments":"Article":private]=>
//  array(2) {
//    [0]=>
//    object(Comment)#5 (0) {
//    }
//    [1]=>
//    object(Comment)#6 (0) {
//    }
//  }
//}

$extendedArticle->clearComments();
var_dump($extendedArticle);
//object(ExtendedArticle)#4 (2) {
//  ["comments":"ExtendedArticle":private]=>
//  array(0) {
//  }
//  ["comments":"Article":private]=>
//  array(0) {
//  }
//}