[Typo3] Making a better access control

[tapio]

Hi

I hope that someone could now help.
I try to create a little bit better access control.
I don't understand the array '$BE_USER' in for exaple db_layout.php
if I use print_r($BE_USER);
a part of the result is '[admin] => 1'
But when I try to print $BE_USER['admin']; it get an empty string!
the seems to be a sub-array, but it is so hard to see the structure of 
the array $BE_USER.

I would try to create content elemen level access control on the base is 
someone is admin user or not.