Novice Ask PHP limit Open Directory related issues

Novice Ask PHP limit Open Directory problem!
I made an open directory of PHP, which has a function to return to the previous level of the directory.
How can I set the user can only open the PHP file in the directory and its sub-record, but not to go back to the PHP file in the directory of the previous level directory it? That is, you can return when you click Back to the previous level, but you can only return to the directory where the PHP file is located and no longer return.
This PHP is very long, not I write, I do not send, because I also do not understand, everyone told me what function, how to do it, of course, the more specific the better.

------Solution--------------------
There's no such function, and you wrote it yourself.
Now that you have a directory move, you should check to see if the new directory has access
------Solution--------------------
Simple, set the user's permissions to execute the PHP process

