title: json data by ajax request is not been sent
body: <p>I want to send json data to php file. when i send it as querystring it ,half of the data is sent and when i send it in the following way then nothing is sent at all</p>
  
  <pre><code> Ext.Ajax.request({
          url: 'GetData.php',
           params: {
              data:document.getElementById("jsonData").value
  
            },
         method: "POST",
  
          contentType: 'application/json; charset=utf-8',
          dataType: 'json',
          success: function(xhr) {
         console.log(xhr)
          }
   });
  </code></pre>
  
  <p>i have modified my ajax call in different ways but it always send null. I have checked that my hiddenfield 'jsonData' has data in it before making ajax request. please help
   here is json data--</p>
  
  <pre><code>{"items":[{"text":"Table of Contents","items":[{"text":"Cover","source":"book/00__Cover.html","leaf":true,"items":"[]"},
  {"text":"Introduction","source":"book/Introduction.html","leaf":true,"items":"[{\"text\":\"Me maps\",\"source\":\"book/Introduction.html#c000030\\\"\",\"leaf\":true},{\"text\":\"Spatial perspective\",\"source\":\"book/Introduction.html#c000031\\\"\",\"leaf\":true}]"},{"text":"Index","source":"book/Index.html","leaf":true,"items":"[]"}]},{"text":"My Study Guide","source":"studyguide.js","leaf":true},{"text":"Shared","source":"shared.js","leaf":true}]}
  </code></pre>