Question about calling PHP functions within a thread

[MoH672]

Ok, so I guess that brings me to a new question.

I've created a new page called calculator.php (at myforums.com/forums/calculator.php) using this tutorial and want to restrict the page to certain usergroups. I have tried the following:

PHP Code:

<?php
if ( $bbuserinfo[usergroupid] == 5 ) {
    echo "<font face='Tahoma' size='4' color='#FFFFFF'>This is 
a test using permissions in PHP.</font>";
}
else {
    echo "<font face='Tahoma' size='4' color='#FFFFFF'>You do 
not have permission to access this page.</font>";
}
?>

But it still returns "You do not have permission to access this page." even though I am in the proper usergroup. What am I doing wrong?