【图】一个简单上传文件出错的解决

以前没怎么注意搞过文件上传，昨天搞了一个简单的却发现问题还挺多。

刚开始的程序代码如下：
uploadimg.php

<?php

//判断是上载界面还是实现界面，如果是上载界面，显示下面的HTML页面
if(!$_POST['UploadAction']):

<html
<head
<title</title
</head
<body<table<center
<form enctype="multipart/form-data" name="SubmitForm" action="" method="post"
<input type="hidden" name="UploadAction" value="1"
<tr<td<input name="UploadFile" type="file" size="30"</td</tr
<tr<td<input type="submit" name="submit" value="上传"</td
<td<input type="reset" name="reset" value="重置"</td</tr
</form
</center</table</body
</html

<?php

//如果是实现页面，显示下面的HTML页面，并激活PHP脚本
else:

<html
<head
<title</title
</head
<body

<?php

//www.knowsky.com初始化UploadAction的状态
$UploadAction=0;

$UploadFile=$_POST['UploadFile'];

if(($UploadFile!="none") && ($UploadFile!=""))
{
$UploadPath=$_SERVER['DOCUMENT_ROOT']."\";

        if (!is_writeable($UploadPath))
        {
                echo "$UploadPath目录不可写!"; exit;
        }
        else
        {
                echo " $UploadPath 目录可写!";
        }

$FileName=$UploadFile_name;

        if($UploadFile_size<1024)
        {
                $FileSize=(string)$UploadFile_size."字节";
        }
        elseif($UploadFile_size<(1024*1024))
        {
                $FileSize=number_format((double)($UploadFile_size/1024),1)."KB";
        }
        else
        {
                $FileSize=number_format((double)($UploadFile_size/(1024*1024)),1)."KB";
        }
        if(!file_exists($UploadPath.$FileName))
        {
                if(move_uploaded_file($UploadFile,$UploadPath.$FileName))
                {
                        echo "文件 $UploadFile_name ($FileSize) 上传成功!";
                }
                else
                {
                        echo "文件 $UploadFile_name ($FileSize) 上传失败!";