source: Dev/trunk/src/client/dojox/form/resources/RecieveFile.php

<?php

// THIS IS AN EXAMPLE
// you will obviously need to do more server side work than I am doing here to check and move your upload.
// API is up for discussion, jump on http://dojotoolkit.org/forums

// JSON.php is available in dojo svn checkout
require("../../../dojo/tests/resources/JSON.php");
$json = new Services_JSON();

// fake delay
sleep(3);
$name = empty($_REQUEST['name'])? "default" : $_REQUEST['name'];
if(is_array($_FILES)){
        $ar = array(
                // lets just pass lots of stuff back and see what we find.
                // the _FILES aren't coming through in IE6 (maybe 7)
                'status' => "success",
                'name' => $name,
                'request' => $_REQUEST,
                'postvars' => $_POST,
                'details' => $_FILES,
                // and some static subarray just to see
                'foo' => array('foo'=>"bar")
        );

}else{
        $ar = array(
                'status' => "failed",
                'details' => ""
        );
}

// yeah, seems you have to wrap iframeIO stuff in textareas?
$foo = $json->encode($ar);
?>
<textarea><?php print $foo; ?></textarea>