Question

I have array in json, but I want to print it in php. I get in post this :

[{"cartData":{"id":"dragged_567737","left":"255px","top":"71px"}},{"cartData":{"id":"dragged_757836","left":"43px","top":"73px"}}]

but when I use print_r($_POST) in my php file, it print me the empty array.
there is my js code:

jQuery('#save_project_data').click( function() {
            var array=[];
            var numItems = $('.icart').length;

            $(".icart").each(function(index) {
                var cart_id = $(this).attr("id");
                var cart_left = $(this).css("left");
                var cart_top = $(this).css("top");

                var cartData = {  
                   "id" : cart_id,                                
                   "left" : cart_left,
                   "top" : cart_top
                };
                queryStr = { "cartData" : cartData };
                array.push(queryStr);
            });

            var postData = JSON.stringify(array);
           $.ajax({
                   url  : "modules/cart_projects/saveData.php",
                   type : "POST",
                   dataType: 'json',
                   contentType: 'application/json; charset=utf-8',

                   data : postData,//{ 'data': '{"name":"chris"}' }
                   traditional: true,
                   success: function(){
                        alert("OK");
                    } 
               });
            return false;
        });

Answer 1

PHP has native support for decoding JSON with json_decode();

$data = json_decode($_POST['myJson']);
print_r($data);

The PHP $_POST array is interpreted from key value pairs, so you need to change your ajax call like below, because your code is sending the post data with no key.

data : { myJson : postData },//{ 'data': '{"name":"chris"}' }

If you change the data structure like above, you need to also remove your application/json; charset=utf-8 content type.

From the Manual:

Takes a JSON encoded string and converts it into a PHP variable.