I found a good way to do this:
In pre.php i created a function that creates $firephp object and then i just call that in show_data.php
---
pre.php
---
require_once($_SERVER['DOCUMENT_ROOT'] . '/intranet/lib/firephp.php');
ob_start();
function mylog($var, $other = '') {
$firephp = FirePHP::getInstance(true);
$firephp->log($var, $other);
}
---
show_data.php
---
include('pre.php')
include('lib/data.php')
mylog('whatever');
This works!