In order to configure your application with debugging, you should include in your bifConfig.inc.php:

$bifcfg['debug']['level'] = 1;

And if you want to output some debugging information in some part of the application:

bif_debug("some debugging info about $var");

You can set different debuging levels, for example:

bif_debug("some verbose debugging info",2);

Reload the page and we'll see that it won't apear, unless you set debug level greater or equal to 2 in your bifConfig.inc.php, that is:

$bifcfg['debug']['level'] = 2;