[Princeton]

PHP Code:

$vbulletin->input->clean_gpc('r', 'page', TYPE_UINT); 


you should get into the habit of "cleaning" any $_GET, $_REQUEST, and $_POST data .... the above is a vb function that cleans/converts data that will be used

if you study the vb files or any product/plugin found here (vb.org) you will find the above line more frequently

This:

PHP Code:

$page = (empty($vbulletin->GPC['page'])) ? 1 : $vbulletin->GPC['page']; 


does the same thing as

PHP Code:

   if(!isset($_GET['page'])){
    $page = 1;
    } else {
    $page = $_GET['page'];
    } 


The ?: operator is used as a shorthand replacement for the if-then-else conditional statement; the general form is condition ? op1 : op2. If condition is true, the statement evaluates as op1; otherwise, it evaluates as op2.