fopen PHP错误(期望参数1为resource)

我正在尝试创建一个目录与PHP文件在它(那部分工作)。

现在我试图打开PHP文件并输入数据，但我得到错误:

警告:fwrite()期望参数1是资源，字符串在C:'wamp'www'dev 3'1'index2.php第13行

和

警告:fclose()期望参数1是资源，字符串在C:'wamp'www'dev 3'1'index2.php第14行

下面是我的代码:

<?php
$directory = substr(md5(rand(1000,10000)),2,8);
mkdir($directory);
$dir = './'.$directory.'/index.php';
$upload = fopen($dir,'x');
$data = '
data data data
';
fopen($dir, "w");
fwrite($dir, $data);
fclose($dir);
?>

<?php
$directory = substr(md5(rand(1000,10000)),2,8);
mkdir($directory);
$dir = './'.$directory.'/index.php';
$upload = fopen($dir,'x');
$data = '
data data data
';
/*fopen($dir, "w");
fwrite($dir, $data);
fclose($dir);
*/
fopen($upload, "w");
fwrite($upload, $data);
fclose($upload);
?>