title: Using uploadifive for multiple file upload causes repeated invocations of check_exists
body: <p>Am using uploadifive (the HTML5 version not the the Flash based uploadify) as follows: </p>
  
  <pre><code>$('#file_upload').uploadifive({ //setup uploadify
      'auto'             : false,
      'removeCompleted'  : true,
      'checkScript'    : 'check-exists.php',
      'formData'         : {
                                'timestamp' : '&lt;?php echo $timestamp;?&gt;',
                                'token'     : '&lt;?php echo md5('unique_salt' . $timestamp);?&gt;'
                           },
      'queueID'          : 'queue',
      'uploader'         : 'uploadifive.php',
      'onUploadFile'     : function(file) {
                              //alert('The file ' + file.name + ' is being uploaded.');
                           },
      'onCheck'          : function(file, exists) {
                             //alert ('onCheck: ' + file.name + '/' + exists);
                           },
      'onUploadComplete'  : function(file, data) { 
                            //alert (file.name + ': ' + data); 
                           }
  });
  </code></pre>
  
  <p>With this simple form:</p>
  
  <pre><code>&lt;form&gt;
      &lt;div id="queue"&gt;&lt;/div&gt;
      &lt;input id="file_upload" name="file_upload" type="file"&gt;
      &lt;a style="position: relative; top: 8px;" href="javascript:$('#file_upload').uploadifive('upload')"&gt;Upload Files&lt;/a&gt;
  &lt;/form&gt;
  </code></pre>
  
  <p>If I load one or two files into an empty folder, all works fine.<br>
  If I load 3 or more I get a variable number of repeated calls to check_info.php. For instance if I upload five files into an empty folder, according to firebug there are 15 calls to check_info.<br>
  1 for file 1, returns 0 (ie file does not exist)<br>
  2 for file 2, both return 0<br>
  3 for file 3, all return 0<br>
  4 for file 4, 1 returns 0 and 3 return 1 (ie file exists)<br>
  5 for file 5, 2 return 0, 3 return 1<br>
  The multiple returns of 0 I can live with (though it's very inefficient) as they are invisible to the user, but the 6 returns of 1, each generate a warning msg to which the user has to respond.<br>
  I have no idea why this happening. Have looked at uploadifive code but it's way beyond my limited knowledge of jQuery.<br>
  Appreciate any advice/suggestions/cures/etc<br>
  Tx in advance</p>