PHP图片上传不上去，出现警告！

上传处理代码：

<?

$f=$_FILES['userfile'];

$type_name= $f['tmp_name'];

//print_r ($_FILES['userfile']);

//有没有传文件判断

if ($f['error']==4){

echo("<script>alert('请选择你要上传的文件，谢谢！');location.href='upfile.php';</script>");

}

else{

//出错判断

if ($f['error']){

echo "失败，文件太大了！错误代码是".$f['error'];

exit;

}



//类型判断

if (substr($f['type'], 0, 5) == 'image') {

                    switch ($f['type']) {

                        case 'image/jpeg':

                        case 'image/jpg':

                        case 'image/pjpeg':

                            $ext = '.jpg';

                            break;

                        case 'image/gif':

                            $ext = '.gif';

                            break;

                        case 'image/png':

                        case 'image/x-png':

                            $ext = '.png';

                            break;

                        default:

                            header('Content-type: text/html; charset=UTF-8');

                            echo("<script>alert('你传的不是图片吧？');location.href='upfile.php';< /script>");

                            die('REDIRECTING...');

                            break;

                    }

}else {

                    header('Content-type: text/html; charset=UTF-8');

                    echo("<script>alert('你传的不是图片吧？');location.href='upfile.php';</script>");

                    die('REDIRECTING...');

                }



//生成随机数

$randomnum=NULL;

for($j=0;$j<=5;$j++)//随机数字的长度，本例随机数长度为6

{

srand((double)microtime()*1000000);

$randomnumber=rand(!$j ? 1: 0,9);//产生随机数，不以0为第一个数，有些特殊的地方0开头被系统省略

$randomnum.=$randomnumber;

}



$dest_dir='/upfile';//设定上传目录



$dest=$dest_dir.'/'.time().'_'.$randomnum.$ext;//设置文件名为时间戳加上随机数避免重复



if (is_uploaded_file($f['tmp_name'])) {	

		$r=move_uploaded_file($_FILES['userfile']['tmp_name'],$dest);

		if($r){

			chmod($dest, 0777);//设定上传的文件的属性

			echo "成功了，文件地址是：".$dest;

		}else{

		

		}

}else{

	echo("<script>alert('上传失败？');location.href='upfile.php';</script>");

}

}

?>

出现的错误：
Warning: move_uploaded_file(/upfile/1297328385_241621.jpg) [function.move-uploaded-file]: failed to open stream: No such file or directory in E:\APMServ5.2.6\www\htdocs\ccc\sysadmin\upload.php on line 61

Warning: move_uploaded_file() [function.move-uploaded-file]: Unable to move 'C:\WINDOWS\temp\php11B.tmp' to '/upfile/1297328385_241621.jpg' in E:\APMServ5.2.6\www\htdocs\ccc\sysadmin\upload.php on line 61

忘高手解答！