performance, memory & objects

Since we are on the topic of objects with PHP, what is the best way to free the memory being used by an object? A lot of examples use unset($objReference). But when freeing the memory used by a large string, it's best to assign that string's reference variable to an empty string, ($str = "";) according to "Programming PHP" by Tatroe and Lerdorf. I was surprised that this book didn't mention freeing memory used by objects (or if I'm wrong, please point me to the right page). Here's a sample from my script I'm working on right now... is assigning the object's reference variable to "null" redundant or not worthwhile? // $result = a MySQL result resource $photos_string = ""; while ($row = mysql_fetch_assoc($result)) { $photo_obj = new PhotoItem($row['photoitem_id']); $photos_string .= $photo_obj->display(); $photo_obj = null; unset($photo_obj); } // do something with $photos_string Erik ---- Erik Price Web Developer Temp Media Lab, H.H. Brown pricee@hhbrown.com