PHP上传文件（学习）

<?php
if(isset($_FILES['upfile']))
{
if (is_uploaded_file($_FILES['upfile']['tmp_name'])){

$upfile=$_FILES["upfile"];

$name = $upfile["name"];
$type = $upfile["type"];
$size = $upfile["size"];
$tmp_name = $upfile["tmp_name"];
$error = $upfile["error"];
$ok=0;
switch($type)
{
case 'image/pjpeg':
$ok=1;
break;
case 'image/jpeg':
$ok=1;
break;
case 'image/gif':
$ok=1;
break;
case 'image/png':
$ok=1;
break;
}
if($ok==1&&$error=='0'){
if(move_uploaded_file($tmp_name,'up/'.$name))
{
echo "上传成功！";
}
}
else{
echo "上传失败。请检查格式";
};
}
}

?>
<form enctype="multipart/form-data" method="post" name="upform">
<input name="upfile" type="file">
<input type="submit" value="上传">
</form>