How to upload files in php and display the upload progress, _PHP tutorial

<&#63;php
$prefix = ini_get('session.upload_progress.prefix');
$name  = ini_get('session.upload_progress.name');
$key  = $prefix . $name;
session_start();
if (isset($_POST['get_info'])) {
  $logo = $prefix . $_POST['logo'];
  exit(json_encode($_SESSION[$logo]));
} elseif ($_POST) {
  echo '<script>var finashed = true;</script>';
}
&#63;>
<div id="show_info_div"></div>
<form action="index.php" method="POST" enctype="multipart/form-data">
  <input type="hidden" name="<&#63;php echo $name; &#63;>" value="test">
  <input type="file" name="file"><br>
  <input type="submit" value="提交">
  <input type="button" value="获取信息" onclick="getUploadInfo()">
</form>
<script src="jquery.js"></script>
<script>
var sto = null;
var progress = null;
function getUploadInfo()
{
  $.post("index.php", {"get_info": 1, "logo": "test"}, function(data)
  {
    data = eval("(" + data + ")");
    progress = parseInt(parseInt(data.bytes_processed) * 10000 / parseInt(data.content_length)) / 100 + "%";
    document.getElementById("show_info_div").innerHTML = progress;
    sto = setTimeout("getUploadInfo()", 1000);
  });
}
if (typeof(finashed) !== "undefined")
{
  document.getElementById("show_info_div").innerHTML = "100.00% (上传成功！)";
}
</script>