// start ouput buffering
ob_start();
// be sure you have uploaded the FirePHP lib on your server
require_once('lib/FirePHPCore/FirePHP.class.php');
// instantiate firephp, false would have turned logging off
$firephp = FirePHP::getInstance(true);
// See some more examples at:
// http://www.firephp.org/HQ/Use.html
$firephp->log('Message','Bob was here');