How to decode JSON string?

Question

PHP

How to decode JSON string?
json_decode - doesn't help.

{"category":"\u041a\u0430\u0431\u0435\u043b\u0438, \u0430\u0434\u0430\u043f\u0442\u0435\u0440\u044b, \u0440\u0430\u0437\u0432\u0435\u0442\u0432\u0438\u0442\u0435\u043b\u0438"}

Answer 1

What does "doesn't help" mean?
php.net/manual/ru/function.json-last-error.php
php.net/manual/ru/function.json-last-error-msg.php

Answer 2

I assume that it's the php version,
since the voiced example worked on my server.
Function description (json_decode) states:
(PHP 5 >= 5.2.0, PECL json >= 1.2.0, PHP 7)