jquery - PHP $_SESSION not working with Fancybox AJAX cal -

i'm having real battle here , hoping out. late last night trying every solution google offered still not had success.

my site has list on ingredients i'd add recipe.

to process is:

1. click "add recipe". opens fancybox iframe containing jquery ui tabbed content allows users enter measurement in grams.

2. from here user clicks "add" , fancybox content makes ajax call (having built data string created fine)..

3. the php file called ajax cast value passed int (of food id , weight) , stores in the:

   $_session['recipe'][] = array('id' => $id , 'weight' => $weight);

4. once complete fancybox closes , div on starting page (step one) contains calorie information recipe should reload , update.

all steps seem work except 3.

whenever try vardump session it's empty.

i've started session on each page, i.e. step 1, the fancybox page, ajax called page.

i'm @ total loss.

my ajax call @ step 3 is:

    $(document).on('click', '.add-food-button', function () {     var weight = $("input#grams").val();       var id = $("input#ingredientid").val();       //var sez = $("input#sez").val();        var datastring = 'g='+ weight +'&id=' + id ; //+ "&sid=" + sez;       if (weight > 0)     {          $.ajax({           type: "post",             url: "../ajax/add-ingredient-to-recipe.php?"+datastring,             datatype: "html",           data: datastring,               success: function (msg) {                   frames.top.$.fancybox.close(true);                 frames.top.$('#calorie-table').load('./views/recipe-calorie-chart.tmp.php');              }          });        }else{           $('#grams').addclass('errorinput');           $('#weight-label').addclass('errorlabel');     }  }); 

and php file called (step 4) is:

<?php  session_start();  include('../includes/config.inc.php');  if (isset($_get['weight']) && $_get['id']) {        $weight = (int) $_get['weight'];     $id = (int) $_get['id'];     $_session['recipe'][] = array('id' => $id,'weight' => $weight);    }  ?> 

i've read passing session id through ajax ajax call generating new session , need using 1 open. if case how do that?

any advice brilliant!

if check ajax call find passing "g" & "id" variable in query string. in php file checking "weight" && "id". condition not true , session never set. getting blank session value.

updated ajax call

$.ajax({       type: "post",         url: "../ajax/add-ingredient-to-recipe.php?"+datastring,         datatype: "html",                    success: function (msg) {               frames.top.$.fancybox.close(true);             frames.top.$('#calorie-table').load('./views/recipe-calorie-chart.tmp.php');          }      }); 

updated php code

    session_start();  include('../includes/config.inc.php');  if (isset($_get['g']) && $_get['id']) {        $weight = (int) $_get['g'];     $id = (int) $_get['id'];     $_session['recipe'][] = array('id' => $id,'weight' => $weight);    }