PHP安全上传图片的方法

<"image.$ext";
move_uploaded_file($_FILES['filename']['tmp_name'], $n);
echo "Uploaded image '$name' as '$n':<br />";
echo "<img src='$n' />";
}
else echo "'$name' is not an accepted image file";
}
else echo "No image has been uploaded";
echo "</body></html>";
?>