Representação JSON do objeto PHP

<?php
class Comment implements jsonSerializable{
public $author;
public $content;
public $date;

public function jsonSerialize(){
return array(
"author" => $this->author,
"content" => $this->content,
"date" => $this->date
);
}
}
$myComment
= new Comment();
$myComment
->author = "Abimael Martell";
$myComment
->content = "Hi there";
$myComment
->date = "2012-11-13 21:06:12";
echo json_encode
($myComment);
//{
// "author":"Abimael Martell",
// "content":"Hi there",
// "date":"2012-11-13 21:06:12"
//}
?>