PHP 警告：move_uploaded_file（） 无法移动

我一直在慢慢学习PHP，并找到了其他开发人员发布的有关该主题和解决方案的一系列信息。我正在尝试让一个Android应用程序通过HTTP post将文件上传到PHP服务器。但是，在我的服务器端有些东西不起作用，试图在PHP中写入文件。

下面是 PHP 代码：

// Where the file is going to be placed
$target_path = "/var/www/media2net/uploads/uploads";

/* Add the original filename to our target path.
Result is "uploads/filename.extension" */
$target_path = $target_path . basename($_FILES['uploadedfile']['name']);

if (move_uploaded_file($_FILES['uploadedfile']['tmp_name'], $target_path)) {
    echo "The file ".  basename( $_FILES['uploadedfile']['name']) .
        " has been uploaded";
    chmod("uploads/" . basename($_FILES['uploadedfile']['name']), 755);
} else {
    echo "There was an error uploading the file, please try again!";
    echo "filename: " . basename( $_FILES['uploadedfile']['name']);
    echo " target_path: " .$target_path;
}

我已经通过检查客户端的wire shark知道http post被正确发送出去，我也确保了我正在编写文件的目录具有正确的权限，并且php安全模式设置为off。

apache2 错误的输出.log文件读取

[Wed Dec 05 09:25:36 2012] [error] [client 74.14.162.250] PHP Warning:  
move_uploaded_file(): Unable to move '/tmp/phpVLOnn3' to  
'/var/www/media2net/uploads/downloaded_file.png' 
in /var/www/media2net/upload.php on line 9

任何有关此问题的帮助或解决此问题的其他方法将不胜感激。