I wrote a blog post about doing this with jQuery to upload a file using a hidden iframe. Here's the code:
Here is the HTML for the form:
<div id="uploadform">
<form id="theuploadform">
<input type="hidden" id="max" name="MAX_FILE_SIZE" value="5000000" >
<input id="userfile" name="userfile" size="50" type="file">
<input id="formsubmit" type="submit" value="Send File" >
</form>
The DIV in which to allow jQuery to create the iframe you can hide it with a little CSS:
<div id="iframe" style="width:0px height:0px visibility:none">
</div>
The DIV in which to show the results of the callback:
<div id="textarea">
</div>
The jQuery code:
<script type="text/javascript" src="js/jquery-1.3.2.min.js"></script>
<script type="text/javascript">
$(document).ready(function(){
$("#formsubmit").click(function() {
var userFile = $('form#userfile').val();
var max = $('form#max').val();
var iframe = $( '<iframe name="postframe" id="postframe" class="hidden" src="about:none" />' );
$('div#iframe').append( iframe );
$('#theuploadform').attr( "action", "uploader.php" )
$('#theuploadform').attr( "method", "post" )
$('#theuploadform').attr( "userfile", userFile )
$('#theuploadform').attr( "MAX_FILE_SIZE", max )
$('#theuploadform').attr( "enctype", "multipart/form-data" )
$('#theuploadform').attr( "encoding", "multipart/form-data" )
$('#theuploadform').attr( "target", "postframe" )
$('#theuploadform').submit();
//need to get contents of the iframe
$("#postframe").load(
function(){
iframeContents = $("iframe")[0].contentDocument.body.innerHTML;
$("div#textarea").html(iframeContents);
}
);
return false;
});
});
</script>
I used a php app like this uploader.php to do something with the file:
<?php
$uploaddir = 'uploads/';
$uploadfile = $uploaddir . basename($_FILES['userfile']['name']);
$maxfilesize = $_POST[MAX_FILE_SIZE];
if ($maxfilesize > 5000000) {
//Halt!
echo "Upload error: File may be to large.<br/>";
exit();
}else{
// Let it go
}
if (move_uploaded_file($_FILES['userfile']['tmp_name'], $uploadfile)) {
print('File is valid, and was successfully uploaded. ');
} else {
echo "Upload error: File may be to large.<br/>";
}
chmod($uploadfile, 0744);
?>
There's more there than you need, but it illustrates the concept in jQuery.