El ejemplo de donde lo saque ponia esto:
<html>
<head>
<title>Ajax File Uploader Plugin For Jquery</title>
<link href="ajaxfileupload.css" type="text/css" rel="stylesheet">
<script type="text/javascript" src="jquery.js"></script>
<script type="text/javascript" src="ajaxfileupload.js"></script>
<script type="text/javascript">
function ajaxFileUpload()
{
$("#loading")
.ajaxStart(function(){
$(this).show();
})
.ajaxComplete(function(){
$(this).hide();
});
$.ajaxFileUpload
(
{
url:'doajaxfileupload.php',
secureuri:false,
fileElementId:'fileToUpload',
dataType: 'json',
data:{name:'logan', id:'id'},
success: function (data, status)
{
if(typeof(data.error) != 'undefined')
{
if(data.error != '')
{
alert(data.error);
}else
{
alert(data.msg);
}
}
},
error: function (data, status, e)
{
alert(e);
}
}
)
return false;
}
</script>
</head>
<body>
<div id="wrapper">
<div id="content">
<h1>Ajax File Upload Demo</h1>
<p>Jquery File Upload Plugin - upload your files with only one input field</p>
<p>
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<img id="loading" src="loading.gif" style="display:none;">
<form name="form" action="" method="POST" enctype="multipart/form-data">
<table cellpadding="0" cellspacing="0" class="tableForm">
<thead>
<tr>
<th>Please select a file and click Upload button</th>
</tr>
</thead>
<tbody>
<tr>
<td><input id="fileToUpload" type="file" size="45" name="fileToUpload" class="input"></td> </tr>
</tbody>
<tfoot>
<tr>
<td><button class="button" id="buttonUpload" onClick="return ajaxFileUpload();">Upload</button></td>
</tr>
</tfoot>
</table>
</form>
</div>
</body>
</html>