How to convert an array to json and get the same array in php?

Question

PHP

Hey! There have already been a lot of things on this topic, but I'm already confused and tried to solve the problem in different ways, but it doesn't work. In general, there is an array and this is ajax:

var cat = ["flats", "underground", "houses"];
        var post_type = $(this).data('post-type');

        $.ajax({
            type : "post",
            context: this,
            dataType : "json",
            url : ajaxurl,
            data : {
                action: "filter_hobby",
                post_type: post_type,
                post_term: JSON.stringify($.extend({}, cat))
            },
            beforeSend: function(data) {
                $('.areas').css('opacity', '1');
            },
            success: function(response) {
                var $newElems = $(response.html);
                $('.areas').html($newElems);

                $('.areas').css('opacity', '1');
            }
        });

Converted to jquery and received in php, but I just can not achieve the desired result.
In php I do like this: But not that, I need the same array ["flats", "underground", "houses"] as output in php. Tell me how to do it? json_decode($_REQUEST['post_term'])

Answer 1

post_term: cat
instead of
post_term: JSON.stringify($.extend({}, cat))