title: Passing values from client to server and back to client, asynchronously
body: <p>I've been trying to figure this problem out for quite a while. I know JavaScript is client side scripting and PHP is server-side scripting, but is it possible to pass a browsers epoch time into a PHP script to run some calculations then return geoJSON data based on the results; all asynchronously?</p>
  
  <p>The function I want to pass to the PHP script is something like:</p>
  
  <pre><code>function retreiveUTC() {
    var now = new Date().getTime();
    var browserUTC = Math.floor(now)/1000.0;  // this returns epoch time of the browser
  }
  </code></pre>
  
  <p>Then I would like to take the epoch time that is generated from the function and pass it to a php script to determine what JSON file to return.</p>
  
  <p>For example I will have the following files residing on the server:</p>
  
  <pre>
  1352188536.JSON
  1352187536.JSON
  1352177536.JSON
  </pre>
  
  <p>And I want to retrieve the one that is closest to the browsers epoch results. Thank you in advance.</p>
  
  <p>Updated code below:</p>
  
  <p>not sure what I am doing wrong, but I am getting success from the ajax call but the return value is undefined.</p>
  
  <p>ajax stuff:</p>
  
  <pre><code>    $.post ('timezone.php',
      {
          epochTime: browserUTC
      }, 
      function (result) {
         //do someting to result
      }, "json");
  
      var browserUTC = new Date().getTime();
  
      $.post ('timezone.php',
      {
          epochTime: browserUTC
      }, 
      function (result,status) {
     //display file name returned by PHP
          alert(result.file + "\n" + status);
     //console.log('test');
      });
  </code></pre>
  
  <p>PHP:</p>
  
  <pre><code>    &lt;?php
      $epochTime = round($_POST['epochTime'] / 1000);
      $res= array();
      $res['file'] = $epochTime . '.JSON';
      return json_encode($res);
      ?&gt;
  </code></pre>