[Help] Code upload ảnh bằng ajax!

<script type="text/javascript">
var swfu;
window.onload = function() {
	var settings = {
	flash_url : "../swfupload/swfupload.swf", //cấu hình đường dẫn file swf
	upload_url: "upload.php", //file xử lý upload ở đây, sửa kích thước cũng ở đây. Xử lý tất...
	post_params: {"PHPSESSID" : "<?php echo session_id(); ?>"},
	file_size_limit : "100 MB", //giới hạn size
	file_types : "*.*", //cho phép loại file nào
	file_types_description : "All Files", 
	file_upload_limit : 100, //giới hạn bao nhiêu file upload cùng 1 lúc
	file_queue_limit : 0,
	custom_settings : {
		progressTarget : "fsUploadProgress",
		cancelButtonId : "btnCancel"
	},
	debug: true,
        //button settings
	button_image_url: "images/TestImageNoText_65x29.png",
	button_width: "65",
	button_height: "29",
	button_placeholder_id: "spanButtonPlaceHolder",
	button_text: '<span class="theFont">Hello</span>',
	button_text_style: ".theFont { font-size: 16; }",
	button_text_left_padding: 12,
	button_text_top_padding: 3,
	// The event handler functions are defined in handlers.js
        //gọi hàm trong file handlers.js đối với các sự kiện
	file_queued_handler : fileQueued,
	file_queue_error_handler : fileQueueError,
	upload_start_handler : uploadStart,
	upload_progress_handler : uploadProgress,
	upload_error_handler : uploadError,
	upload_success_handler : uploadSuccess
//...
</script>

<?php
	if (isset($_POST["PHPSESSID"])) {
		session_id($_POST["PHPSESSID"]);
	}
	session_start();

	// The Demos don't save files


	// In this demo we trigger the uploadError event in SWFUpload by returning a status code other than 200 (which is the default returned by PHP)
	if (!isset($_FILES["Filedata"]) || !is_uploaded_file($_FILES["Filedata"]["tmp_name"]) || $_FILES["Filedata"]["error"] != 0) {
		// Usually we'll only get an invalid upload if our PHP.INI upload sizes are smaller than the size of the file we allowed
		// to be uploaded.
		header("HTTP/1.1 500 File Upload Error");
		if (isset($_FILES["Filedata"])) {
			echo $_FILES["Filedata"]["error"];
		}
		exit(0);
	}
	
	echo "Make sure Flash Player on OS X works";
?>