[Admin]

  $findwords=array(0 => '{getmicrostats}', 1 => '{bbusername}');
  $replacewords=array(0 => $microstats, 1 => "$bbuserinfo[username]<!-- auto name hack -->");
  $i=1;
  while ($var=$DB_site->fetch_array($vars) and $i++) {
    if ($var['findword']!='') {
      $findwords[$i]=$var['findword'];
      $replacewords[$i]=$var['replaceword'];
    }
  }
  $newtext=str_replace($findwords,$replacewords,$newtext);

Might work.