Asynschronous HTML File Upload (fake Ajax)

upload-form.html

<script language="javascript" type="text/javascript">
function formUploadCallback (result) {
    console.log("Upload OK:", result);
    alert('Upload OK');
}
</script>
<form target="upload_target" action="upload.php" enctype="multipart/form-data" method="post">
File: <input name="myfile" type="file" />
<input name="submitBtn" type="submit" value="Submit" />
</form>
<iframe id="upload_target" name="upload_target" src="#" style="width:0;height:0;border:0px solid #fff;"></iframe> 

upload.php

<script language="javascript" type="text/javascript">
window.top.window.formUploadCallback(<?php echo $result; ?>);
</script>