消息：mkdir（）：codeigniter上的权限被拒绝

i have error when creating folder by using mkdir() on my codeigniter getting this error:

Message: mkdir(): Permission denied

and this my code

$path = './upload_file/';
$idtrx = $_POST['id_trx'];
$dir = $path.$idtrx;
mkdir($dir,0777,TRUE);

can anyone helps me??

Hope this will help you :

$file_path = FCPATH.'upload_file/'.$_POST['id_trx'];

if(!is_dir($file_path)) @mkdir($file_path, 0777, true);