子目录没有创建在PHP中

I am trying to create a sub directory in PHP, but it's created in the root directory, not in the destination directory:

if($_SERVER['REQUEST_METHOD']=='POST') {
    $dirName = $_POST['dirname'];
    $path = $_POST['PATH'];
    $dir = "../apps/Assamese_Songs/".$path."/" .$dirName."/";
    if (mkdir($dir, 0777, true)) {
        //header('Location: folder_manager.php');
    }
}

Every time the directory is created in Assamese_Songs directory, but I want it created in $path.