js php xmlrequest 上传图片

本来想用插件上传图片的，后来自己写了一个简单的js实现异步的图片上传，不多说上代码非常简单

upload.php

if(isset($_FILES["myfile"]))
{
$ret = array();
$uploadDir = 'images'.DIRECTORY_SEPARATOR.date("Ymd").DIRECTORY_SEPARATOR;
$dir = dirname(__FILE__).DIRECTORY_SEPARATOR.$uploadDir;
file_exists($dir) || (mkdir($dir,0777,true) && chmod($dir,0777));
if(!is_array($_FILES["myfile"]["name"])) //single file
{
$fileName = time().uniqid().'.'.pathinfo($_FILES["myfile"]["name"])['extension'];
move_uploaded_file($_FILES["myfile"]["tmp_name"],$dir.$fileName);
$ret['file'] = DIRECTORY_SEPARATOR.$uploadDir.$fileName;
}
echo json_encode($ret);
}

?>

index.html

<script type="text/javascript">


var xhr;
function createXMLHttpRequest()
{
if(window.ActiveXObject)
{
xhr = new ActiveXObject("Microsoft.XMLHTTP");
}
else if(window.XMLHttpRequest)
{
xhr = new XMLHttpRequest();
}
}


function UpladFile()
{
var fileObj = document.getElementById("file").files[0];
var FileController = 'upload.php';
var form = new FormData();
form.append("myfile", fileObj);
createXMLHttpRequest();
xhr.onreadystatechange = handleStateChange;
xhr.open("post", FileController, true);
xhr.send(form);
}


function handleStateChange()
{
if(xhr.readyState == 4)
{
if (xhr.status == 200 || xhr.status == 0)
{
var result = xhr.responseText;
var json = eval("(" + result + ")");
alert('图片链接:/n'+json.file);
}
}
}


</script>