title: Ajax request takes too long
body: <p>I'm asking you, because I dont have any ideas...</p>
  
  <p>I've made an ajax request which gets a small data from the server. The json answer is already cached by the server, so it's pretty fast.</p>
  
  <p>Like</p>
  
  <pre><code>window.xhr = $.ajax({
  url: domain+'index.php?fx_action=ajax&amp;fx_mode=continents&amp;fx_type=countries&amp;fx_ajaxid='+window.currentajaxrequest+'&amp;fx_id='+window.id+'&amp;fx_page='+(window.page-1)+'&amp;fx_pager='+window.pager+'&amp;fx_order='+window.order,
  type: 'POST',
  dataType: 'json',
  timeout: 5000,
  cache: false,
  async: true,
  beforeSend: function () {
          ...
      },
      error: function (xhr, ajaxOptions, thrownError) {
          return false;
      },
      success: function (data) {  
          ...
  </code></pre>
  
  <p>But the answer time is sliding on a huge scale, sometimes it takes for 1 sec sometimes just 67 millisecs...</p>
  
  <pre><code>continents.js:65  http://teszt.domain.com/index.php?fx_action=ajax&amp;fx_mode=continents&amp;fx_type=countries&amp;fx_ajaxid=0&amp;fx_id=6&amp;fx_page=1&amp;fx_pager=9&amp;fx_order=name
  continents.js:100 start: 0
  continents.js:101 beforesend: 9
  continents.js:102 success: 5087
  continents.js:103 complete: 5096
  continents.js:65  http://teszt.domain.com/index.php?fx_action=ajax&amp;fx_mode=continents&amp;fx_type=countries&amp;fx_ajaxid=1&amp;fx_id=6&amp;fx_page=2&amp;fx_pager=9&amp;fx_order=name
  continents.js:100 start: 0
  continents.js:101 beforesend: 9
  continents.js:102 success: 70
  continents.js:103 complete: 77
  continents.js:65  http://teszt.domain.com/index.php?fx_action=ajax&amp;fx_mode=continents&amp;fx_type=countries&amp;fx_ajaxid=2&amp;fx_id=6&amp;fx_page=3&amp;fx_pager=9&amp;fx_order=name
  continents.js:100 start: 0
  continents.js:101 beforesend: 11
  continents.js:102 success: 301
  continents.js:103 complete: 304
  </code></pre>
  
  <p>In getting the same data structure with almost same size in kbytes. And everything is cached by the server.</p>
  
  <p>In the server side the php's running time always about 30-40ms. What is my mistake?</p>